This work was funded by the Wellcome Trust (WT098051).

<ol>
	<li>Goudreault, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+PP2A+phosphatase+high+density+interaction+network+identifies+a+novel+striatin-interacting+phosphatase+and+kinase+complex+linked+to+the+cerebral+cavernous+malformation+3+(CCM3)+protein.">A PP2A phosphatase high density interaction network identifies a novel striatin-interacting phosphatase and kinase complex linked to the cerebral cavernous malformation 3 (CCM3) protein.</a> Mol Cell Proteomics. 8 (1), 157-171 (2009).</li><li>Leitner, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+native+protein+structures+by+chemical+cross-linking,+mass+spectrometry,+and+bioinformatics.">Probing native protein structures by chemical cross-linking, mass spectrometry, and bioinformatics.</a> Mol Cell Proteomics. 9 (8), 1634-1649 (2010).</li><li>Rappsilber, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+beginning+of+a+beautiful+friendship:+cross-linking/mass+spectrometry+and+modelling+of+proteins+and+multi-protein+complexes.">The beginning of a beautiful friendship: cross-linking/mass spectrometry and modelling of proteins and multi-protein complexes.</a> J Struct Biol. 173 (3), 530-540 (2011).</li><li>Sinz, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+cross-linking+and+mass+spectrometry+to+map+three-dimensional+protein+structures+and+protein-protein+interactions.">Chemical cross-linking and mass spectrometry to map three-dimensional protein structures and protein-protein interactions.</a> Mass Spectrom Rev. 25 (4), 663-682 (2006).</li><li>Walzthoeni, T., Leitner, A., Stengel, F., Aebersold, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mass+spectrometry+supported+determination+of+protein+complex+structure.">Mass spectrometry supported determination of protein complex structure.</a> Curr Opin Struct Biol. 23 (2), 252-260 (2013).</li><li>Kaake, R. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+in+vivo+cross-linking+mass+spectrometry+platform+to+define+protein-protein+interactions+in+living+cells.">A new in vivo cross-linking mass spectrometry platform to define protein-protein interactions in living cells.</a> Mol Cell Proteomics. 13 (12), 3533-3543 (2014).</li><li>Kao, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+novel+cross-linking+strategy+for+fast+and+accurate+identification+of+cross-linked+peptides+of+protein+complexes.">Development of a novel cross-linking strategy for fast and accurate identification of cross-linked peptides of protein complexes.</a> Mol Cell Proteomics. 10 (1), (2011).</li><li>Hughes, M. A., Langlais, C., Cain, K., MacFarlane, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation,+characterisation+and+reconstitution+of+cell+death+signalling+complexes.">Isolation, characterisation and reconstitution of cell death signalling complexes.</a> Methods. 61 (2), 98-104 (2013).</li><li>Lim, S., Zou, Y., Friedman, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+transcriptional+activator+Mirk/Dyrk1B+is+sequestered+by+p38alpha/beta+MAP+kinase.">The transcriptional activator Mirk/Dyrk1B is sequestered by p38alpha/beta MAP kinase.</a> J Biol Chem. 277 (51), 49438-49445 (2002).</li><li>Havugimana, P. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+census+of+human+soluble+protein+complexes.">A census of human soluble protein complexes.</a> Cell. 150 (5), 1068-1081 (2012).</li><li>Kirkwood, K. J., Ahmad, Y., Larance, M., Lamond, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+native+protein+complexes+and+protein+isoform+variation+using+size-fractionation-based+quantitative+proteomics.">Characterization of native protein complexes and protein isoform variation using size-fractionation-based quantitative proteomics.</a> Mol Cell Proteomics. 12 (12), 3851-3873 (2013).</li><li>Kristensen, A. R., Gsponer, J., Foster, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+high-throughput+approach+for+measuring+temporal+changes+in+the+interactome.">A high-throughput approach for measuring temporal changes in the interactome.</a> Nat Methods. 9 (9), 907-909 (2012).</li><li>Liu, F., Heck, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interrogating+the+architecture+of+protein+assemblies+and+protein+interaction+networks+by+cross-linking+mass+spectrometry.">Interrogating the architecture of protein assemblies and protein interaction networks by cross-linking mass spectrometry.</a> Curr Opin Struct Biol. 35, 100-108 (2015).</li><li>Wittig, I., Schagger, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Native+electrophoretic+techniques+to+identify+protein-protein+interactions.">Native electrophoretic techniques to identify protein-protein interactions.</a> Proteomics. 9 (23), 5214-5223 (2009).</li><li>Heide, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complexome+profiling+identifies+TMEM126B+as+a+component+of+the+mitochondrial+complex+I+assembly+complex.">Complexome profiling identifies TMEM126B as a component of the mitochondrial complex I assembly complex.</a> Cell Metab. 16 (4), 538-549 (2012).</li><li>Wessels, H. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+953+human+proteins+from+a+mitochondrial+HEK293+fraction+by+complexome+profiling.">Analysis of 953 human proteins from a mitochondrial HEK293 fraction by complexome profiling.</a> PLoS One. 8 (7), 68340 (2013).</li><li>Wessels, H. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=LC-MS/MS+as+an+alternative+for+SDS-PAGE+in+blue+native+analysis+of+protein+complexes.">LC-MS/MS as an alternative for SDS-PAGE in blue native analysis of protein complexes.</a> Proteomics. 9 (17), 4221-4228 (2009).</li><li>Remmerie, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unraveling+tobacco+BY-2+protein+complexes+with+BN+PAGE/LC-MS/MS+and+clustering+methods.">Unraveling tobacco BY-2 protein complexes with BN PAGE/LC-MS/MS and clustering methods.</a> J Proteomics. 74 (8), 1201-1217 (2011).</li><li>Sessler, N., Krug, K., Nordheim, A., Mordmuller, B., Macek, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+the+Plasmodium+falciparum+proteasome+using+Blue+Native+PAGE+and+label-free+quantitative+mass+spectrometry.">Analysis of the Plasmodium falciparum proteasome using Blue Native PAGE and label-free quantitative mass spectrometry.</a> Amino Acids. 43 (3), 1119-1129 (2012).</li><li>Bode, D., Yu, L., Tate, P., Pardo, M., Choudhary, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+Two+Distinct+Nucleosome+Remodeling+and+Deacetylase+(NuRD)+Complex+Assemblies+in+Embryonic+Stem+Cells.">Characterization of Two Distinct Nucleosome Remodeling and Deacetylase (NuRD) Complex Assemblies in Embryonic Stem Cells.</a> Mol Cell Proteomics. 15 (3), 878-891 (2016).</li><li>Cox, J., Mann, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MaxQuant+enables+high+peptide+identification+rates,+individualized+p.p.b.-range+mass+accuracies+and+proteome-wide+protein+quantification.">MaxQuant enables high peptide identification rates, individualized p.p.b.-range mass accuracies and proteome-wide protein quantification.</a> Nat Biotechnol. 26 (12), 1367-1372 (2008).</li><li>Cox, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+practical+guide+to+the+MaxQuant+computational+platform+for+SILAC-based+quantitative+proteomics.">A practical guide to the MaxQuant computational platform for SILAC-based quantitative proteomics.</a> Nat Protoc. 4 (5), 698-705 (2009).</li><li>Kim, J. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+regulatory+factor+recruits+the+nucleosome+remodeling+complex+to+wingless+integrated+(Wnt)+signaling+gene+promoters+in+mouse+embryonic+stem+cells.">A novel regulatory factor recruits the nucleosome remodeling complex to wingless integrated (Wnt) signaling gene promoters in mouse embryonic stem cells.</a> J Biol Chem. 287 (49), 41103-41117 (2012).</li><li>Lauberth, S. M., Rauchman, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+conserved+12-amino+acid+motif+in+Sall1+recruits+the+nucleosome+remodeling+and+deacetylase+corepressor+complex.">A conserved 12-amino acid motif in Sall1 recruits the nucleosome remodeling and deacetylase corepressor complex.</a> J Biol Chem. 281 (33), 23922-23931 (2006).</li><li>Miller, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sall4+controls+differentiation+of+pluripotent+cells+independently+of+the+Nucleosome+Remodelling+and+Deacetylation+(NuRD)+complex.">Sall4 controls differentiation of pluripotent cells independently of the Nucleosome Remodelling and Deacetylation (NuRD) complex.</a> Development. 143 (17), 3074-3084 (2016).</li><li>Dharmarajan, V., Lee, J. H., Patel, A., Skalnik, D. G., Cosgrove, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+basis+for+WDR5+interaction+(Win)+motif+recognition+in+human+SET1+family+histone+methyltransferases.">Structural basis for WDR5 interaction (Win) motif recognition in human SET1 family histone methyltransferases.</a> J Biol Chem. 287 (33), 27275-27289 (2012).</li><li>Schwanhausser, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Global+quantification+of+mammalian+gene+expression+control.">Global quantification of mammalian gene expression control.</a> Nature. 473 (7347), 337-342 (2011).</li><li>Smits, A. H., Jansen, P. W., Poser, I., Hyman, A. A., Vermeulen, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stoichiometry+of+chromatin-associated+protein+complexes+revealed+by+label-free+quantitative+mass+spectrometry-based+proteomics.">Stoichiometry of chromatin-associated protein complexes revealed by label-free quantitative mass spectrometry-based proteomics.</a> Nucleic Acids Res. 41 (1), 28 (2013).</li><li>Lambert, J. P., Tucholska, M., Pawson, T., Gingras, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Incorporating+DNA+shearing+in+standard+affinity+purification+allows+simultaneous+identification+of+both+soluble+and+chromatin-bound+interaction+partners.">Incorporating DNA shearing in standard affinity purification allows simultaneous identification of both soluble and chromatin-bound interaction partners.</a> J Proteomics. 100, 55-59 (2014).</li><li>Wittig, I., Braun, H. P., Schagger, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blue+native+PAGE.">Blue native PAGE.</a> Nat Protoc. 1 (1), 418-428 (2006).</li><li>Schagger, H., Cramer, W. A., von Jagow, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+molecular+masses+and+oligomeric+states+of+protein+complexes+by+blue+native+electrophoresis+and+isolation+of+membrane+protein+complexes+by+two-dimensional+native+electrophoresis.">Analysis of molecular masses and oligomeric states of protein complexes by blue native electrophoresis and isolation of membrane protein complexes by two-dimensional native electrophoresis.</a> Anal Biochem. 217 (2), 220-230 (1994).</li><li>Schagger, H., von Jagow, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blue+native+electrophoresis+for+isolation+of+membrane+protein+complexes+in+enzymatically+active+form.">Blue native electrophoresis for isolation of membrane protein complexes in enzymatically active form.</a> Anal Biochem. 199 (2), 223-231 (1991).</li><li>Camacho-Carvajal, M. M., Wollscheid, B., Aebersold, R., Steimle, V., Schamel, W. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+Blue+native/SDS+gel+electrophoresis+of+multi-protein+complexes+from+whole+cellular+lysates:+a+proteomics+approach.">Two-dimensional Blue native/SDS gel electrophoresis of multi-protein complexes from whole cellular lysates: a proteomics approach.</a> Mol Cell Proteomics. 3 (2), 176-182 (2004).</li><li>Liu, F., Rijkers, D. T., Post, H., Heck, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteome-wide+profiling+of+protein+assemblies+by+cross-linking+mass+spectrometry.">Proteome-wide profiling of protein assemblies by cross-linking mass spectrometry.</a> Nat Methods. 12 (12), 1179-1184 (2015).</li></ol>

The authors have nothing to disclose.

Hier beschreiben wir die Verwendung von Affinitätsreinigung gefolgt von blau native Gelelektrophorese in Kombination mit quantitativen Massenspektrometrie Proteinkomplexe aufzulösen. Dieser Ansatz bietet eine Methode eindimensional Protein-Wechselwirkung Listen in funktionelle Proteinkomplexe zu entwirren. Wir zeigen das Verfahren basiert auf der Verwendung von Epitop-markierten Proteinen. Wenn jedoch eine Zelllinie ein markiertes Protein exprimieren, nicht verfügbar ist, könnte eine Alternative sein, Antikörper gegen das Protein von Interesse zu verwenden, sofern ein Peptid zur Verfügung nativen kompetitive Elution zu erreichen. Die Menge des Ausgangsmaterials und der Menge der Perlen kann in Abhängigkeit von dem Expressionsspiegel des Zielproteins werden müssen modifiziert. Wir führen in der Regel dieses Protokoll mit 2-5 x 10 8 Zellen - Ausgangsmaterial, und dies ist ausreichend , um auch die für Proteine mit niedrigem Expressionsniveau. Die Lysepuffer Zusammensetzung sollte empirisch gewählt werden, um zu erreichen,in der Nähe von vollständiger Auflösung des Köders. Dies kann für einige Arten von Proteinen, insbesondere Chromatin-Bindung oder Membranproteine ​​schwierig sein. Alternative Optionen gehören die Erhöhung die Menge an Salz, vorausgesetzt , daß der Proteinkomplex in Untersuchung in hohem Salz stabil ist, oder unter Verwendung von Ultraschall - Behandlung und / oder Nuklease - Behandlung für Chromatin - Bindungsproteine 20, 29. Im Falle von Membranproteinen, können Waschmittel DDM oder Digitonin Schalt 30 sinnvoll sein. Im Fall von DNA - Bindungsproteinen, ist es sinnvoll , eine Nuklease Benzonase wie während der Reinigungsstufe 20 umfasst. Die vollständige Entfernung von Nukleinsäuren gewährleistet, dass die detektierten Wechselwirkungen zwischen Proteinen auftreten und nicht durch DNA vermittelt. Ein kritisches Element zu berücksichtigen, wenn mit diesem Ansatz die Stabilität des Komplexes untersucht wird. Das Verfahren ist lang und preservin beinhalten kanng der Proteinkomplex über Nacht. Wir haben gute Erfolge mit zwei Chromatin-Remodeling-Komplexe (D. Bode und M. Pardo, Daten nicht gezeigt) erreicht, aber dies ausgewertet werden soll. Der Affinitätsreinigungsschritt kann bei Bedarf gekürzt werden. Alternative Techniken, die native Fraktionierung ermöglichen, wie Grßenausschlußchromatographie, sind seit mehr als 50 Jahren zu charakterisieren Proteinkomplexe weit verbreitet. Wir und andere haben gezeigt , dass die Auflösung der blauen native PAGE auf , dass 20, 31, 32, 33 unter Verwendung von Grßenausschlußchromatographie erreicht überlegen ist. Ein weiterer Vorteil der blauen native PAGE ist, dass es nicht Chromatographie-Systeme erfordert, die teuer sind, sondern nutzt Protein elektrophoretische Geräte, die in Laboratorien weit verbreitet ist. In Bezug auf die Hands-on-Zeit, diese Methode beinhaltet nicht mehr Arbeit als die traditionelle GELC-MS / MS einNSATZ oder offline chromatographische Fraktionierung. Da jedoch die meisten Fraktionierungsverfahren tun, hat es eine Grenze für ihre Auflösung. Komplexe, die sehr homogen oder in der Nähe in Masse und Form sind, können über die Auflösung von blau native PAGE angeboten werden, und somit das Protokoll wie hier berichtete nicht sein könnte allgemein erfolgreich bei der Lösung verschiedene Komplexe mit gemeinsamen Untereinheiten. Erfreulicherweise haben wir bei der Trennung von zwei sehr ähnliche tetramere Komplexe teilen drei Untereinheiten (M. Pardo, Manuskript in Vorbereitung) erfolgreich. Da Massenspektrometrie zunehmend empfindlich geworden ist, auch kleinste Mengen an unspezifischer Interaktoren und Verunreinigungen können in AP-MS Proben nachgewiesen werden. Der hier vorgestellte Ansatz könnte bei der Unterscheidung von echten Interaktionspartner von Hintergrundbelastung in der Affinitätsreinigung helfen, indem die Aufmerksamkeit auf Proteine ​​mit Migrationsspitzen zu konzentrieren, die als bei höheren Molekulargewicht mit Ködern Migration Spitzen zusammenfallen, dass diedie monomeren Proteine. Mehrere Gruppen haben Fraktionierungstechniken durch Protein - Korrelationsprofilierungs gefolgt verwendet , um Protein - Komplexe auf Zell Maßstab ohne die Notwendigkeit einer vorherigen Isolierung 10, 11, 12, 34 abzugrenzen. Dies kann jedoch dazu führen, substöchiometrischen Wechselwirkungen zu erkennen. Der Einbau eines Anreicherungsschritt durch Affinitätsreinigung kann helfen, diese zu überwinden. Der hier beschriebene Ansatz sollte für die Erkundung der Topologie von Proteinkomplexen und Entschlüsselung der mehrere Komplexe ein bestimmtes Protein an innerhalb der gleichen zellulären Kontext dauert in der Regel nützlich sein. Die Strategie ist einfach und zugänglich für Laboratorien, die nicht teuer chromatographische Fraktionierung Ausrüstung können Proteinkomplexe zu lösen.

In Zellen, führen die meisten Proteine ​​ihre Funktionen durch transitorische Protein-Protein-Wechselwirkungen oder durch stabile Proteinanordnungen bilden. Protein-Wechselwirkungen charakterisierenden ist für voll Verständnis zellulärer Prozesse von entscheidender Bedeutung. Affinitätsreinigung in Kombination mit der Massenspektrometrie (AP-MS) ist eine der am häufigsten angewandt Strategien native Protein-Wechselwirkungen zu identifizieren. Signifikante Verbesserungen in den Instrumenten Fähigkeiten in den letzten zehn Jahren erreicht haben, diesen Ansatz extrem leistungsfähig gemacht. Es ist wichtig zu beachten, dass die von AP-MS-Experimenten identifiziert Wechselwirkungen eine Mischung aus direkten und indirekten Verbindungen zwischen Köder und Beute sind. Darüber hinaus oft Proteine ​​nehmen an mehreren verschiedenen Komplexen innerhalb des gleichen zellulären Kontext, die unterschiedliche biologische Rollen haben könnte, und daher sind die Interaktoren, die durch AP-MS identifiziert werden könnte eine Mischung von verschiedenen Protein-Baugruppen oder Funktionseinheiten darstellen. Es ist nicht möglich abzuleitensolche topologischen Informationen a priori aus den mono-dimensional Listen von Proteinen durch einfache AP-MS - Experimente erzeugt. Jedoch kann die Technik ausgenutzt werden, um die Architektur weiter von Proteinkomplexen zu definieren, indem sie mit einer oder mehreren Methoden, die Kombination dieser Baugruppen zu lösen. Um haben die Topologie von Protein-Wechselwirkungen identifiziert durch AP-MS, verschiedene Strategien angewandt worden zu lösen. Ein Ansatz ist die iterativen AP-MS - Experimente durchzuführen , unter Verwendung des in einer früheren Runde von Experimenten identifiziert preys als Köder 1. Obwohl sehr informativ, ist dies eine Arbeit ganz Aufgabe intensiv experimentell und analytisch. Protein Vernetzung in Kombination mit der Massenspektrometrie wird zunehmend eingesetzt, um 2 auf den Proteinkomplexen topologische Informationen abzuleiten, 3, 4, 5. Allerdings computational Analyse von vernetzten Peptide bleibt nach wie vor eine schwierige Aufgabe, und daher ist der Engpass im Arbeitsablauf. Das Aufkommen von MS-spaltbare Vernetzungsreagenzien sollten Kartierung der Aminosäurereste erleichtern , die 6 Proteine in enger Nähe sind, 7 in zusammenwirkt. Eine weitere Alternative ist die Affinitätsreinigung des Standes der orthogonalen Trenntechniken zu kombinieren 8, 9. Chromatographische Fraktionierung durch Gelfiltration oder Ionenaustausch oder Saccharosegradienten - Fraktionierung wird kürzlich auch in Kombination mit quantitativer Massenspektrometrie verwendet Multiproteinkomplexe in einer systemweiten Ebene zu beschreiben, unter Umgehung des komplexen Isolierungsschrittes 10, 11, 12, 13. Blau nativen Polyacrylamid-Gelelektrophorese (BN-PAGE) wurde in großem Umfang angewendetuntersuchen native Protein - Wechselwirkungen, Protein typischerweise mitochondrialen Membrankomplexe solcher , die 14. Diese Trenntechnik wurde kürzlich auch in Kombination mit markierungsfreien Proteinquantifizierung und Korrelations Profilieren, nicht nur auf die mitochondriale Komplexe 15, 16, 17, sondern auch für andere entwirren Proteinkomplexe aus ganzen Zellen 18, 19 verwendet. Wir stellten die Hypothese, dass die Kombination von Affinitätsreinigung mit anschließenden nativen Fraktionierung Ansätzen und quantitativem MS sollte für die Lösung mehrerer Proteineinheiten eine nützliche Strategie bietet ein bestimmtes Protein enthalten. Hier beschreiben wir ein Verfahren, das generische Epitop-basierte Affinitätsreinigung mit blauem nativer Polyacrylamidgelelektrophorese der isolierten Komplexe, gefolgt von quantitativen Massen sp vereintectrometry und Proteinkorrelationsprofilerstellung, die mehrere Baugruppen ein Protein lösen könnten beteiligt werden. Wir embryonalen Stammzellen der Maus verwenden, wo ein Protein von Interesse an ein Epitop-Tag fusioniert ist, von dem endogenen Locus exprimiert physiologischen Fülle der Nähe zu erreichen und effizient nativen gewährleisten Komplex Isolation. Dieser Ansatz entwirrt die mehrere Wechselwirkungen ein Protein eingreift, so dass sie in verschiedene Baugruppen auf ihre Korrelationsprofile basierend Lösung, während erfordern keine Arbeit mehr als herkömmliche GELC-MS 20.

<table border="0" cellpadding="0" cellspacing="0" width="1384">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">Protein G Dynabeads</td>
			<td style="width:285px;">Life Technologies</td>
			<td style="width:220px;">10003D</td>
			<td style="width:452px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">FLAG antibody M2</td>
			<td style="width:285px;">Sigma-Aldrich</td>
			<td style="width:220px;">F1804</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">Tween-20, protein grade, 10% solution</td>
			<td style="width:285px;">Millipore</td>
			<td style="width:220px;">655206</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">Dimethyl pimelimidate</td>
			<td style="width:285px;">Sigma-Aldrich</td>
			<td style="width:220px;">80490</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">0.2 M Triethanolamine buffer, pH 8.2</td>
			<td style="width:285px;">Sigma-Aldrich</td>
			<td style="width:220px;">T0449</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">3x FLAG peptide</td>
			<td style="width:285px;">Sigma-Aldrich</td>
			<td style="width:220px;">F4799</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">Vivaspin 5K NMWCO, PES</td>
			<td style="width:285px;">Sartorius</td>
			<td style="width:220px;">VS0112</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">NativePAGE 3-12% Bis-Tris gel</td>
			<td style="width:285px;">Life Technologies</td>
			<td style="width:220px;">BN1001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">20x NativePAGE Running Buffer</td>
			<td style="width:285px;">Life Technologies</td>
			<td style="width:220px;">BN2001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">20x NativePAGE Cathode Additive</td>
			<td style="width:285px;">Life Technologies</td>
			<td style="width:220px;">BN2002</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">4x NativePAGE sample loading buffer</td>
			<td style="width:285px;">Life Technologies</td>
			<td style="width:220px;">BN2003</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">NativeMARK</td>
			<td style="width:285px;">Life Technologies</td>
			<td style="width:220px;">LC0725</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NativePAGE 5% G-250 sample additive&#160;</td>
			<td style="width:285px;">Life Technologies</td>
			<td style="width:220px;">BN2004</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">Nunc conical bottom 96-well plate, polypropylene</td>
			<td style="width:285px;">Thermo</td>
			<td style="width:220px;">249944</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">Multiscreen HTS 96-well filtration system</td>
			<td style="width:285px;">Thermo</td>
			<td style="width:220px;">MSDVN6550</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">Nunc 96-well cap natural</td>
			<td style="width:285px;">Thermo</td>
			<td style="width:220px;">276002</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">TCEP (Tris(2-carboxyethyl)phosphine hydrochloride)</td>
			<td style="width:285px;">Sigma-Aldrich</td>
			<td style="width:220px;">646547</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">Iodoacetamide</td>
			<td style="width:285px;">Sigma-Aldrich</td>
			<td style="width:220px;">I1149</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">Acetonitrile, HPLC grade</td>
			<td style="width:285px;">Fisher Scientific</td>
			<td style="width:220px;">A/0627/17</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">Trypsin, sequencing grade</td>
			<td style="width:285px;">Roche</td>
			<td style="width:220px;">11418475001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">Software</td>
			<td style="width:285px;"></td>
			<td style="width:220px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">MaxQuant (software)</td>
			<td style="width:285px;">N.A.</td>
			<td style="width:220px;">N.A.</td>
			<td style="width:452px;">http://www.biochem.mpg.de/5111795/maxquant</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:427px;">Perseus (software)</td>
			<td style="width:285px;">N.A.</td>
			<td style="width:220px;">N.A.</td>
			<td style="width:452px;">http://www.biochem.mpg.de/5111810/perseus</td>
		</tr>
	</tbody>
</table>

resolving affinity purified protein complexes by blue native page and protein correlation profiling

Most proteins act in association with others; hence, it is crucial to characterize these functional units in order to fully understand biological processes. Affinity purification coupled to mass spectrometry (AP-MS) has become the method of choice for identifying protein-protein interactions. However, conventional AP-MS studies provide information on protein interactions, but the organizational information is lost. To address this issue, we developed a strategy to unravel the distinct functional assemblies a protein might be involved in, by resolving affinity-purified protein complexes prior to their characterization by mass spectrometry. Protein complexes isolated through affinity purification of a bait protein using an epitope tag and competitive elution are separated through blue native electrophoresis. Comparison of protein migration profiles through correlation profiling using quantitative mass spectrometry allows assignment of interacting proteins to distinct molecular entities. This method is able to resolve protein complexes of close molecular weights that might not be resolved by traditional chromatographic techniques such as gel filtration. With little more work than conventional AP-geLC-MS/MS, we demonstrate this strategy may in many cases be adequate for obtaining protein complex topological information concomitantly to identifying protein interactions.

Der Arbeitsablauf der Affinitätsreinigung Blau native Protein Correlation Profilierung durch Massenspektrometrie (ABC-MS) Strategie ist in Abbildung 7 dargestellt. Native Protein-Komplexe um ein Protein von Interesse werden durch Affinitätsreinigung isoliert Antikörper gegen einen Epitop-Tag (in diesem Fall FLAG) und kompetitive Elution mit. Die Komplexe werden durch BN-PAGE aufgetrennt, und die ganze Gelspur ist in 48 Abschnitte herausgeschnitten und für Schrot LC-MS / MS. Quantitative MS Informationen werden verwendet, um ein Migrationsprofil für jedes identifizierte Protein über die blaue nativen Trennung zu erzeugen. Proteine, die interagieren, ein deutliches komplexe Anzeige ähnliche Migrationsprofile mit deckungs Spitzen bilden. Wenn ein Protein von Interesse an mehr als eine Baugruppe erfolgt, werden mehrere Peaks in ihrem Migrationsprofil beobachtet, da die Teilkomplexe sind innerhalb des Auflösungsvermögens des blauen nativen Gels. Ein systematischer Vergleich der migRation Profile können durch Protein-Korrelation erreicht werden Profilierungs hierarchische Clustern unter Verwendung. Das Dendrogramm und die Spitzenintensitäten für alle Fraktionen werden in einem wärme Karte visualisiert, erleichtert die Identifizierung Proteinen in Wechselwirkung zu treten, die auf unterschiedliche Proteinkomplexen gehören (Abbildung 8). Wir nutzten diese Strategie , um die Interaktionspartner von MTA2 zu analysieren, eine Kernuntereinheit der NuRD Chromatin - Komplex 20 Umbau. Wie in 9 gezeigt ist , zeigte das Migrationsprofil von MTA2 zwei Peaks unterschiedlicher Intensitäten zwischen 700 kDa und 1,2 MDa, mit der unteren Massenspitze höher Fülle anzeigt. Andere NuRD Kern - Untereinheiten, einschließlich MTA1 / 3, HDAC1 / 2 und MBD3 identisches Trennungsmuster zeigten, wenn auch Peaks , das für einige der Untereinheiten, nämlich CHD4, Gatad2a / b und Rbbp4 / 7, hatten die inverse Häufigkeitsverteilung (9A, B). Im Gegensatz dazu das Profil von Cdk2ap1, ein Regulationsfaktor, der den Komplex zu NuRD Wnt Genpromotoren rekrutiert 23, dargestellt nur die höheren Massenpeak (Abbildung 9C), und so hat Sall4, einen transkriptionalen Repressor, der auch 20 NuRD zu binden , gezeigt worden ist, 24, 25. Somit Fraktionierung von affinitätsgereinigtem MTA2-assoziierte Proteine, die durch blaue native PAGE konnte zwei verschiedene Formen des NuRD Komplex lösen. ABC-MS ermöglicht auch die Identifizierung von neuen Interaktoren, während sie zu bestimmten Protein Einheiten zuweisen. Durch Untersuchung der Proteine Cluster und Fraktion in einer Wärme Karte dargestellt Intensitäten detektiert wir eine starke Korrelation zwischen Untereinheiten und NuRD WDR5, eine regulatorischen Untereinheit des MLL - Methyltransferase - Komplexes 26 mit WDR5 Anzeige von zwei Migrations Peaks mit dem beide NuRD p koinzidenteaks (Abbildung 8), eine neuartige Wechselwirkung zwischen WDR5 und NuRD hindeutet. Wir bestätigten diese Interaktion durch Co-Immunpräzipitation und Co-Migration in Grßenausschlußchromatographie 20. Die Auswahl der Abstandsmetrik-Berechnung in dem hierarchischen Clustering wird die Form der Cluster beeinflussen und damit die Zusammenhänge. Wir empfehlen, mit den verschiedenen Metriken experimentieren die beste Lösung mit bestehenden Interaktion Wissen des Proteins oder ein Komplex von Interesse zu erreichen. Im allgemeinen erreicht man die besten Ergebnisse mit der Manhattan (L1) Distanzmaß 20. Pearson - Korrelation oder euklidische Abstandsmetriken sind auch zur Identifizierung von Komplexen basierend auf alternative Fraktionierungstechniken 10 berichtet, 11, 12. die quantitative MS Daten aus den blauen nativen erhaltenen Fraktionen können auch die Stöchiometrie von Proteinkomplexen zu bestimmen, verwendet werden. Die iBAQ (Intensität basierend absolute Quantifizierung) -Wert liefert ein Maß für die relative Häufigkeit der identifizierten Proteine 27, 28. Die iBAQ Werte für die Protein-Komplex Mitglieder in allen Fraktionen innerhalb einer peak Migrationsprofil sind, dass der Köder-Protein normalisiert relativen Mengen zu erhalten. Die normalisierten iBAQs über eine Profilspitze für ein Protein-Komplex gegeben Element sollten einen horizontalen Trend folgen, und die Trendwerte spiegeln die Stöchiometrie der interagierenden Proteine ​​relativ zu dem Köder-Protein. Für eine detailliertere Darstellung der Stöchiometrie Berechnungen, siehe 20. <img alt="Abbildung 7" src="/files/ftp_upload/55498/55498fig7.jpg" /> Abbildung 7: Schematische Workflow einer Zusammenfassung der ABC-MS strategie. Diese Zahl wird aus 20 modifiziert ist . <a href="http://ecsource.jove.com/files/ftp_upload/55498/55498fig7large.jpg" target="_blank">Bitte klicken Sie hier</a> , um <a href="http://ecsource.jove.com/files/ftp_upload/55498/55498fig7large.jpg" target="_blank">eine größere Version dieser Figur zu sehen.</a> <img alt="Abbildung 8" src="/files/ftp_upload/55498/55498fig8.jpg" /> Abbildung 8. Hierarchical Clustering von BN-PAGE Migrationsprofile der MTA2 Interaktoren. MTA2-assoziierte Proteine ​​wurden auf der Grundlage der Ähnlichkeit ihrer Migrationsprofile gruppierten. Nur eine Teilmenge der wärme Karte des NuRD Komplex enthält, wird (eingeschlossen in der blauen Box) gezeigt. Das gelbe Feld unterstreicht die starke Korrelation von WDR5 mit dem NuRD Komplex. Die kommentierten Molekulargewichte wurden aus den Wanderungsstrecken von Proteinstandards in demselben Gel laufen geschätzt. Diese Forschung wurde ursprünglich in Molecular and Cellular Proteomics 20 der amerikanischen Gesellschaft für Biochemie und Mo veröffentlicht<html> molekulare Biologie. <a href="http://ecsource.jove.com/files/ftp_upload/55498/55498fig8large.jpg" target="_blank">Bitte klicken Sie hier</a> , um <a href="http://ecsource.jove.com/files/ftp_upload/55498/55498fig8large.jpg" target="_blank">eine größere Version dieser Figur zu sehen.</a> <img alt="9" src="/files/ftp_upload/55498/55498fig9.jpg" /> Abbildung 9. BN-PAGE Migrationsprofil von NuRD Untereinheiten und assoziierten Proteinen. A) MTA2 und NuRD Untereinheiten , die in einem ähnlichen Intensitätsmuster. B) MTA2 und NuRD Untereinheiten mit dem inversen Intensitätsmuster. C) MTA2 und Cdk2ap1, die in der höheren Molekulargewicht NuRD Entität nur vorhanden ist. Die kommentierten Molekulargewichte wurden aus dem Migrationsprofil der Proteinstandards geschätzt. Diese Forschung wurde ursprünglich in Molecular and Cellular Proteomics 20 der amerikanischen Gesellschaft für Biochemie und Molekularbiologie veröffentlicht._blank &quot;&gt; Bitte hier klicken, um eine größere Version dieser Figur zu sehen. <img alt="Supplemental Datei" src="/files/ftp_upload/55498/proteinGroupsDB04.jpg" /> Ergänzende Daten: Beispieldatensatz. MaxQuant abgeleitete proteingroups.txt Datei Protein Identifikationen und Quantifizierungswerte von einem ABC-MS-Experiment enthält. Diese Forschung wurde ursprünglich in Molecular and Cellular Proteomics 20 der amerikanischen Gesellschaft für Biochemie und Molekularbiologie veröffentlicht. <a href="https://www.jove.com/files/ftp_upload/55498/proteinGroupsDB04.txt" target="_blank">Bitte klicken Sie hier</a> , um <a href="https://www.jove.com/files/ftp_upload/55498/proteinGroupsDB04.txt" target="_blank">diese Datei herunterzuladen.</a>

Watch this Scientific Journal Video about Resolving Affinity Purified Protein Complexes by Blue Native PAGE and Protein Correlation Profiling at JoVE.com

Resolving Affinity Purified Protein Complexes by Blue Native PAGE and Protein Correlation Profiling

Hier stellen wir Protokolle für die Affinitätsreinigung von Proteinkomplexen und deren Trennung durch blaue native PAGE, gefolgt von Proteinkorrelationsprofilierungs freie quantitative Massenspektrometrie Label. Diese Methode ist nützlich Interaktom in verschiedene Proteinkomplexe zu lösen.

Auflösen von Affinity Purified Protein-Komplexen von Blue native PAGE und Protein Correlation Profilieren

Most proteins act in association with others; hence, it is crucial to characterize these functional units in order to fully understand biological ...

resolving-affinity-purified-protein-complexes-blue-native-page

Research

JoVE Journal

Biochemistry

13.7K Aufrufe.  Wellcome Trust Sanger Institute.  Hier stellen wir Protokolle für die Affinitätsreinigung von Proteinkomplexen und deren Trennung durch blaue native PAGE, gefolgt von Proteinkorrelationsprofilierungs freie quantitative Massenspektrometrie Label. Diese Methode ist nützlich Interaktom in verschiedene Proteinkomplexe zu lösen. 

Serie: Resolving Affinity Purified Protein Complexes by Blue Native PAGE and Protein Correlation Profiling

Protein Complex Affinity Capture from Cryomilled Mammalian Cells

Affinity capture is an effective technique for isolating endogenous protein complexes for further study. When used in conjunction with an antibody, this technique is also frequently referred to as immunoprecipitation. Affinity capture can be applied in a bench-scale and in a high-throughput context. When coupled with protein mass spectrometry, affinity capture has proven to be a workhorse of interactome analysis. Although there are potentially many ways to execute the numerous steps involved, the following protocols implement our favored methods. Two features are distinctive: the use of cryomilled cell powder to produce cell extracts, and antibody-coupled paramagnetic beads as the affinity medium. In many cases, we have obtained superior results to those obtained with more conventional affinity capture practices. Cryomilling avoids numerous problems associated with other forms of cell breakage. It provides efficient breakage of the material, while avoiding denaturation issues associated with heating or foaming. It retains the native protein concentration up to the point of extraction, mitigating macromolecular dissociation. It reduces the time extracted proteins spend in solution, limiting deleterious enzymatic activities, and it may reduce the non-specific adsorption of proteins by the affinity medium. Micron-scale magnetic affinity media have become more commonplace over the last several years, increasingly replacing the traditional agarose- and Sepharose-based media. Primary benefits of magnetic media include typically lower non-specific protein adsorption; no size exclusion limit because protein complex binding occurs on the bead surface rather than within pores; and ease of manipulation and handling using magnets.

Here we describe protocols to disrupt mammalian cells by solid-state milling at a cryogenic temperature, produce a cell extract from the resulting cell powder, and isolate protein complexes of interest by affinity capture upon antibody-coupled micron-scale paramagnetic beads.

Protein Complex Affinity Capture von Cryomilled Mammalian Cells

Affinity capture is an effective technique for isolating endogenous protein complexes for further study. When used in conjunction with an antibody, this ...

Forschung

Biochemie

Tandem Affinity Purification of Protein Complexes from Eukaryotic Cells

The purification of active protein-protein and protein-nucleic acid complexes is crucial for the characterization of enzymatic activities and de novo identification of novel subunits and post-translational modifications. Bacterial systems allow for the expression and purification of a wide variety of single polypeptides and protein complexes. However, this system does not enable the purification of protein subunits that contain post-translational modifications (e.g., phosphorylation and acetylation), and the identification of novel regulatory subunits that are only present/expressed in the eukaryotic system. Here, we provide a detailed description of a novel, robust, and efficient tandem affinity purification (TAP) method using STREP- and FLAG-tagged proteins that facilitates the purification of protein complexes with transiently or stably expressed epitope-tagged proteins from eukaryotic cells. This protocol can be applied to characterize protein complex functionality, to discover post-translational modifications on complex subunits, and to identify novel regulatory complex components by mass spectrometry. Notably, this TAP method can be applied to study protein complexes formed by eukaryotic or pathogenic (viral and bacterial) components, thus yielding a wide array of downstream experimental opportunities. We propose that researchers working with protein complexes could utilize this approach in many different ways.

We describe here a novel, robust, and efficient tandem affinity purification (TAP) method for the expression, isolation, and characterization of protein complexes from eukaryotic cells. This protocol could be utilized for the biochemical characterization of discrete complexes as well as the identification of novel interactors and post-translational modifications that regulate their function.

Tandem Affinity Purification von Proteinkomplexen aus eukaryotischen Zellen

The purification of active protein-protein and protein-nucleic acid complexes is crucial for the characterization of enzymatic activities and de novo ...

Multimer-PAGE: A Method for Capturing and Resolving Protein Complexes in Biological Samples

There are many well-developed methods for purifying and studying single proteins and peptides. However, most cellular functions are carried out by networks of interacting protein complexes, which are often difficult to investigate because their binding is non-covalent and easily perturbed by purification techniques. This work describes a method of stabilizing and separating native protein complexes from unmodified tissue using two-dimensional polyacrylamide gel electrophoresis. Tissue lysate is loaded onto a non-denaturing blue-native polyacrylamide gel, then an electric current is applied until the protein migrates a short distance into the gel. The gel strip containing the migrated protein is then excised and incubated with the amine-reactive cross-linking reagent dithiobis(succinimidyl propionate), which covalently stabilizes protein complexes. The gel strip containing cross-linked complexes is then cast into a sodium dodecyl sulfate polyacrylamide gel, and the complexes are separated completely. The method relies on techniques and materials familiar to most molecular biologists, meaning it is inexpensive and easy to learn. While it is limited in its ability to adequately separate extremely large complexes, and has not been universally successful, the method was able to capture a wide variety of well-studied complexes, and is likely applicable to many systems of interest.

A method for stabilizing and separating native protein complexes from unmodified tissue lysate using an amine-reactive protein cross-linker coupled to a novel two-dimensional polyacrylamide gel electrophoresis (PAGE) system is presented.

Multimer-PAGE: Ein Verfahren zum Erfassen und Auflösen von Proteinkomplexen in biologischen Proben

There are many well-developed methods for purifying and studying single proteins and peptides. However, most cellular functions are carried out by ...

Horizontal Gel Electrophoresis for Enhanced Detection of Protein-RNA Complexes

Native polyacrylamide gel electrophoresis is a fundamental tool of molecular biology that has been used extensively for the biochemical analysis of RNA-protein interactions. These interactions have been traditionally analyzed with polyacrylamide gels generated between two glass plates and samples electrophoresed vertically. However, polyacrylamide gels cast in trays and electrophoresed horizontally offers several advantages. For example, horizontal gels used to analyze complexes between fluorescent RNA substrates and specific proteins can be imaged multiple times as electrophoresis progresses. This provides the unique opportunity to monitor RNA-protein complexes at several points during the experiment. In addition, horizontal gel electrophoresis makes it possible to analyze many samples in parallel. This can greatly facilitate time course experiments as well as analyzing multiple reactions simultaneously to compare different components and conditions. Here we provide a detailed protocol for generating and using horizontal native gel electrophoresis for analyzing RNA-Protein interactions.

Native polyacrylamide gel electrophoresis is a fundamental tool for analyzing RNA-protein interactions. Traditionally most experiments have used vertical gels. However, horizontal gels provide several advantages, such as the opportunity to monitor complexes during electrophoresis. We provide a detailed protocol for generating and using horizontal native gel electrophoresis.

Horizontale Gel-Elektrophorese zur verbesserten Nachweis von Protein-RNA-Komplexen

Native polyacrylamide gel electrophoresis is a fundamental tool of molecular biology that has been used extensively for the biochemical analysis of ...

Split-BioID &#8212; Proteomic Analysis of Context-specific Protein Complexes in Their Native Cellular Environment

To complement existing affinity purification (AP) approaches for the identification of protein-protein interactions (PPI), enzymes have been introduced that allow the proximity-dependent labeling of proteins in living cells. One such enzyme, BirA* (used in the BioID approach), mediates the biotinylation of proteins within a range of approximately 10 nm. Hence, when fused to a protein of interest and expressed in cells, it allows the labeling of proximal proteins in their native environment. As opposed to AP that relies on the purification of assembled protein complexes, BioID detects proteins that have been marked within cells no matter whether they are still interacting with the protein of interest when they are isolated. Since it biotinylates proximal proteins, one can moreover capitalize on the exceptional affinity of streptavidin for biotin to very efficiently isolate them. While BioID performs better than AP for identifying transient or weak interactions, both AP- and BioID-mass spectrometry approaches provide an overview of all possible interactions a given protein may have. However, they do not provide information on the context of each identified PPI. Indeed, most proteins are typically part of several complexes, corresponding to distinct maturation steps or different functional units. To address this common limitation of both methods, we have engineered a protein-fragments complementation assay based on the BirA* enzyme. In this assay, two inactive fragments of BirA* can reassemble into an active enzyme when brought in close proximity by two interacting proteins to which they are fused. The resulting split-BioID assay thus allows the labeling of proteins that assemble around a pair of interacting proteins. Provided these two only interact in a given context, split-BioID then allows the analysis of specific context-dependent functional units in their native cellular environment. Here, we provide a step-by-step protocol to test and apply split-BioID to a pair of interacting proteins.

We provide a step-by-step protocol for split-BioID, a protein fragments-complementation assay based on the proximity-labeling technique BioID. Activated on the interaction of two given proteins, it allows the proteomics analysis of context-dependent protein complexes in their native cellular environment. The method is simple, cost-effective and only requires standard laboratory equipment.

Split-BioID — Proteomic Analyse der kontextspezifischen Proteinkomplexe in ihrer natürlichen zellulären Umgebung

To complement existing affinity purification (AP) approaches for the identification of protein-protein interactions (PPI), enzymes have been introduced ...

2 in 1: One-step Affinity Purification for the Parallel Analysis of Protein-Protein and Protein-Metabolite Complexes

Cellular processes are regulated by interactions between biological molecules such as proteins, metabolites, and nucleic acids. While the investigation of protein-protein interactions (PPI) is no novelty, experimental approaches aiming to characterize endogenous protein-metabolite interactions (PMI) constitute a rather recent development. Herein, we present a protocol that allows simultaneous characterization of the PPI and PMI of a protein of choice, referred to as bait. Our protocol was optimized for Arabidopsis cell cultures and combines affinity purification (AP) with mass spectrometry (MS)-based protein and metabolite detection. In short, transgenic Arabidopsis lines, expressing bait protein fused to an affinity tag, are first lysed to obtain a native cellular extract. Anti-tag antibodies are used to pull down protein and metabolite partners of the bait protein. The affinity-purified complexes are extracted using a one-step methyl tert-butyl ether (MTBE)/methanol/water method. Whilst metabolites separate into either the polar or the hydrophobic phase, proteins can be found in the pellet. Both metabolites and proteins are then analyzed by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS or UPLC-MS/MS). Empty-vector (EV) control lines are used to exclude false positives. The major advantage of our protocol is that it enables identification of protein and metabolite partners of a target protein in parallel in near-physiological conditions (cellular lysate). The presented method is straightforward, fast, and can be easily adapted to biological systems other than plant cell cultures.

Protein-protein and protein-metabolite interactions are crucial for all cellular functions. Herein, we describe a protocol that allows parallel analysis of these interactions with a protein of choice. Our protocol was optimized for plant cell cultures and combines affinity purification with mass spectrometry-based protein and metabolite detection.

2 in 1: Affinitätsreinigung für die parallele Analyse von Protein-Protein und Protein-Metabolit komplexe in einem Schritt

Cellular processes are regulated by interactions between biological molecules such as proteins, metabolites, and nucleic acids. While the investigation of ...

Analysis of Thylakoid Membrane Protein Complexes by Blue Native Gel Electrophoresis

Photosynthetic electron transfer chain (ETC) converts solar energy to chemical energy in the form of NADPH and ATP. Four large protein complexes embedded in the thylakoid membrane harvest solar energy to drive electrons from water to NADP+ via two photosystems, and use the created proton gradient for production of ATP. Photosystem PSII, PSI, cytochrome b6f (Cyt b6f) and ATPase are all multiprotein complexes with distinct orientation and dynamics in the thylakoid membrane. Valuable information about the composition and interactions of the protein complexes in the thylakoid membrane can be obtained by solubilizing the complexes from the membrane integrity by mild detergents followed by native gel electrophoretic separation of the complexes. Blue native polyacrylamide gel electrophoresis (BN-PAGE) is an analytical method used for the separation of protein complexes in their native and functional form. The method can be used for protein complex purification for more detailed structural analysis, but it also provides a tool to dissect the dynamic interactions between the protein complexes. The method was developed for the analysis of mitochondrial respiratory protein complexes, but has since been optimized and improved for the dissection of the thylakoid protein complexes. Here, we provide a detailed up-to-date protocol for analysis of labile photosynthetic protein complexes and their interactions in Arabidopsis thaliana.

A protocol for the elucidation of plant thylakoid protein complex organization and composition with blue native polyacrylamide gel electrophoresis (BN-PAGE) and 2D-SDS-PAGE is described. The protocol is optimized for Arabidopsis thaliana, but can be used for other plant species with minor modifications.

Analyse der Thylakoidmembran Membran-Protein-komplexe durch blaue Native Gelelektrophorese

Photosynthetic electron transfer chain (ETC) converts solar energy to chemical energy in the form of NADPH and ATP. Four large protein complexes embedded ...

Affinity Purification of Chloroplast Translocon Protein Complexes Using the TAP Tag

Chloroplast biogenesis requires the import of thousands of nucleus-encoded proteins into the plastid. The import of these proteins depends on the translocon at the outer (TOC) and inner (TIC) chloroplast membranes. The TOC and TIC complexes are multimeric and probably contain yet unknown components. One of the main goals in the field is to establish the complete inventory of TOC and TIC components. For the isolation of TOC-TIC complexes and the identification of new components, the preprotein receptor TOC159 has been modified N-terminally by the addition of the tandem affinity purification (TAP) tag resulting in TAP-TOC159. The TAP-tag is designed for two sequential affinity purification steps (hence "tandem affinity"). The TAP-tag used in these studies consists of a N-terminal IgG-binding domain derived from Staphylococcus aureus Protein A (ProtA) followed by a calmodulin-binding peptide (CBP). Between these two affinity tags, a tobacco etch virus (TEV) protease cleavage site has been included. Therefore, TEV protease can be used for gentle elution of TOC159-containing complexes after binding to IgG beads. In the protocol presented here, the second Calmodulin-affinity purification step was omitted. The purification protocol starts with the preparation and solubilization of total cellular membranes. After the detergent-treatment, the solubilized membrane proteins are incubated with IgG beads for the immunoisolation of TAP-TOC159-containing complexes. Upon binding and extensive washing, TAP-TOC159 containing complexes are cleaved and released from the IgG beads using the TEV protease whereby the S. aureus IgG-binding domain is removed. Western blotting of the isolated TOC159-containing complexes can be used to confirm the presence of known or suspected TOC and TIC proteins. More importantly, the TOC159-containing complexes have been used successfully to identify new components of the TOC and TIC complexes by mass spectrometry. The protocol that we present potentially allows the efficient isolation of any membrane-bound protein complex to be used for the identification of yet unknown components by mass spectrometry.

We here present a proven and tested protocol for the purification of chloroplast protein import complexes (TOC-TIC complex) using the TAP-tag. The one-step affinity-isolation protocol can potentially be applied to any protein and be used to identify new interaction partners by mass spectrometry.

Affinitätsreinigung der Chloroplasten Translocon Proteinkomplexe mit dem TAP-Tag

Chloroplast biogenesis requires the import of thousands of nucleus-encoded proteins into the plastid. The import of these proteins depends on the ...

High Sensitivity Measurement of Transcription Factor-DNA Binding Affinities by Competitive Titration Using Fluorescence Microscopy

Accurate quantification of transcription factor (TF)-DNA interactions is essential for understanding the regulation of gene expression. Since existing approaches suffer from significant limitations, we have developed a new method for determining TF-DNA binding affinities with high sensitivity on a large scale. The assay relies on the established fluorescence anisotropy (FA) principle but introduces important technical improvements. First, we measure a full FA competitive titration curve in a single well by incorporating TF and a fluorescently labeled reference DNA in a porous agarose gel matrix. Unlabeled DNA oligomer is loaded on the top as a competitor and, through diffusion, forms a spatio-temporal gradient. The resulting FA gradient is then read out using a customized epifluorescence microscope setup. This improved setup greatly increases the sensitivity of FA signal detection, allowing both weak and strong binding to be reliably quantified, even for molecules of similar molecular weights. In this fashion, we can measure one titration curve per well of a multi-well plate, and through a fitting procedure, we can extract both the absolute dissociation constant (KD) and active protein concentration. By testing all single-point mutation variants of a given consensus binding sequence, we can survey the entire binding specificity landscape of a TF, typically on a single plate. The resulting position weight matrices (PWMs) outperform those derived from other methods in predicting in vivo TF occupancy. Here, we present a detailed guide for implementing HiP-FA on a conventional automated fluorescent microscope and the data analysis pipeline.

Here we present a novel method for determining binding affinities at equilibrium and in solution with high sensitivity on a large scale. This improves the quantitative analysis of transcription factor-DNA binding. The method is based on automated fluorescence anisotropy measurements in a controlled delivery system.

Hohe Empfindlichkeit Messung der Transkription Faktor-DNA verbindlichen Affinitäten durch wettbewerbsfähige Titration mit Fluoreszenz-Mikroskopie

Accurate quantification of transcription factor (TF)-DNA interactions is essential for understanding the regulation of gene expression. Since existing ...

Analysis of Protein Folding, Transport, and Degradation in Living Cells by Radioactive Pulse Chase

Radioactive pulse-chase labeling is a powerful tool for studying the conformational maturation, the transport to their functional cellular location, and the degradation of target proteins in live cells. By using short (pulse) radiolabeling times (&lt;30 min) and tightly controlled chase times, it is possible to label only a small fraction of the total protein pool and follow its folding. When combined with nonreducing/reducing SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoprecipitation with (conformation-specific) antibodies, folding processes can be examined in great detail. This system has been used to analyze the folding of proteins with a huge variation in properties such as soluble proteins, single and multi-pass transmembrane proteins, heavily N- and O-glycosylated proteins, and proteins with and without extensive disulfide bonding. Pulse-chase methods are the basis of kinetic studies into a range of additional features, including co- and posttranslational modifications, oligomerization, and polymerization, essentially allowing the analysis of a protein from birth to death. Pulse-chase studies on protein folding are complementary with other biochemical and biophysical methods for studying proteins in vitro by providing increased temporal resolution and physiological information. The methods as described within this paper are adapted easily to study the folding of almost any protein that can be expressed in mammalian or insect-cell systems.

Here we describe a protocol for a general pulse-chase method that allows the kinetic analysis of folding, transport, and degradation of proteins to be followed in live cells.

Analyse der Proteinfaltung, Transport und Abbau in lebenden Zellen durch radioaktive Puls Chase

Radioactive pulse-chase labeling is a powerful tool for studying the conformational maturation, the transport to their functional cellular location, and ...