Wir danken Stephan Wilkens für Hilfe in Transmissions-Elektronenmikroskopie. Diese Arbeit wurde von den National Institutes of Health Grants R01AG023731 unterstützt.

Frühere Studien haben gezeigt, dass die ersten 22 aminoterminalen Reste von Mgm101 nach dem Import in Mitochondrien 19 gespalten werden. Zur Expression in Escherichia coli, wird das MGM101 offenen Leserahmen ohne die ersten 22 Codons durch PCR amplifiziert und hinter die männlichen Sequenz, die das Maltose-bindende Protein (MBP) in einer modifizierten Version des Expressionsvektors pMAL-C2E platziert. Dies erzeugt die MBP-Mgm101 Fusion mit einem Linker, der eine Spaltstelle für die Protease PreScission (Abbildung 3). Das Plasmid wird zunächst durch Auswahl E. konstruiert coli Transformanten ohne IPTG und X-Gal blau / weiß-Selektion. Das resultierende Plasmid pMAL-C2E-MGM101 wird dann in den E. eingeführt coli-Stamm BL21-CodonPlus (DE3)-RIL indem Sie Ampicillin und Chloramphenicol-resistenten Kolonien. 1. Expression, Induktion, Cell Lysis und DNase I Behandlung <ol><li> InocUlate frisch Transformanten in 10 ml LB-Medium (1% Bacto Trypton, 0,5% Hefeextrakt, 1% NaCl) mit Glucose (0,2%), Ampicillin (100 ug / ml) und Chloramphenicol (50 ug / ml) ergänzt. Bei 37 ° CO / N unter Schütteln bei 200 rpm inkubiert. </li><li> Impfen die 10 ml Vorkultur in 2 Liter des ergänzten LB-Medium wie oben. Wachsen die Zellen bei 37 ° C unter Schütteln bis OD 600 erreicht 0,5. </li><li> Induzieren der Expression von MBP-Mgm101 Fusionsproteins durch Zugabe von Isopropyl-β-D-1-thiogalactopyranosid (IPTG) in einer Endkonzentration von 0,3 mM. Wachsen die Zellen unter Schütteln bei 30 ° C für 5 Stunden. </li><li> Sammeln der Zellen durch Zentrifugation unter Verwendung eines Beckman JA-10-Rotor (5.500 × g, 4 ° C, 10 min). Nachdem der Überstand verworfen, das Zellpellet in 30 ml Lysepuffer (20 mM Tris-HCl, pH 7,4 und 1 mM EDTA, pH 7,4), der Protease-Inhibitoren (25 uM Leupeptin, 1 uM Pepstatin A und 1 mM PMSF). </li><li> Beschallen Zellsuspension auf Eis für 20sec mit einem Ultraschall-Prozessor (Heat Systems; Modell W-385) bei 50% ED, ermöglichen, sich auf Eis für 30 sec abkühlen und 2x wiederholen. </li><li> 1 ml DNAse 1 stock bei 2 mg / ml. Rock the Zelllysat bei 4 ° C für 2 Stunden. </li><li> Stellen NaCl bis zu einer Endkonzentration von 500 mM. </li><li> Entfernen der Zelltrümmer durch Zentrifugation bei 10.000 × g bei 4 ° C für 30 min. </li></ol> 2. Reinigung mit Amylose-Affinitätschromatographie <ol><li> Äquilibrieren 1,5 ml Amylose-Harz (50% Suspension) in dem Lysepuffer. Fügen Sie das Gleichgewicht Amyloseharz dem Zelllysat. Schaukeln sanft bei 4 ° CO / N. </li><li> Legen Sie das Lysat-Harz-Mischung auf einer Econo-Column Chromatographie-Säule in einem kalten Raum installiert. Lassen Sie die ungebundenen Proteine, um die Spalte durch die Schwerkraft passieren. </li><li> Waschen der Amylose-Harz mit 300 ml Waschpuffer I (20 mM Tris-HCl, pH 7,4, 400 mM NaCl, 1 mM EDTA, pH 7,4 und 0,2 mM PMSF). </li><li> Wiederholen Sie die Wäsche mit 150 ml Waschpuffer II (20 mM Tris-HCl, pH 7,4, 200 mM NaCl, 1 mM EDTA, pH 7,4 und 0,2 mM PMSF). </li><li> 5 ml Elutionspuffer (20 mM Tris-HCl, pH 7,4, 200 mM NaCl, 1 mM EDTA, pH 7,4 und 0,2 mM PMSF, 10 mM Maltose) auf die Säule bei 4 ° C inkubiert für 10 Minuten, Sammeln das Eluat und wiederholen Sie für weitere Male. </li><li> Kombinieren der Eluate, bestimmen die Ausbeute und Reinheit der MBP-Mgm101 durch Laden eines Aliquots des Eluats auf einem SDS-PAGE-Gel von Coomassie-Färbung (Abbildung 4). </li></ol> 3. PreScission Proteasespaltung und Kationenaustausch-Chromatographie <ol><li> In 50 Einheiten PreScission Protease an die MBP-Mgm101 Eluat. Führen die Spaltung bei 4 ° CO / N und lassen es während der Dialyse gegen Dialysepuffer weiter (20 mM Tris-HCl, pH 7,4; 100 mM NaCl; 2 mM DTT, 1 mM EDTA, pH 7,4 und 0,2 mM PMSF) </li><li> Prüfen Sie die Effizienz der Spaltung auf einem SDS-PAGE-Gel (Abbildung 5A). </li><li> Legen Sie das gespaltene MBP-Mgm101 von mehreren injizierenIonen auf einem Bio-Maßstab Mini Macro-Prep Hohe S Patrone zu einem Bio-Rad Biologic DuoFlow FPLC-System verbunden. </li><li> Starten Sie den Kationenaustauscherchromatographie durch Anlegen einer Schritt Salzgradient von 5 mm, 300 mm, 500 mm, 750 mm und 1000 mM NaCl, die durch Mischen von Puffer A (5 mM NaCl erstellt wird; 10 mM Na-Phosphat, pH 7,2; 1 mM PMSF) und Puffer B (1 M NaCl; 10 mM Na-Phosphat, pH 7,2; 1 mM PMSF). Stellen Sie den Durchfluss bei 0,5 ml / min. Sammeln Sie die Mgm101 Fraktion und überprüfen Sie die Reinheit des Proteins auf einem SDS-PAGE-Gel (Abbildung 5B). </li></ol> 4. Size Exclusion Chromatography <ol><li> Kombinieren Sie die Proteinfraktionen aus Kationenaustauscherchromatographie. Dialyse des Proteins in GF Äquilibrierungspuffer (20 mM MOPS, pH 7,0; 150 mM NaCl; 1 mM EDTA, pH 7,4, 5 mM 2-Mercaptoethanol, 0,2 mM PMSF). </li><li> Konzentrieren des Proteins mit VIVASPIN 15R Ultrafiltration Spin-Säule, um die Lautstärke zu ~ 1 ml durch Spinnen bei 3.000 xg bei 4 ° C reduzieren </li><li> Legen Mgm101 ona kalibriert Superose 6 prep Grad Säule, die mit dem Chromatographie-Puffer (20 mM MOPS, pH 7,0; 150 mM NaCl; 5 mM β-Mercaptoethanol, 1 mM EDTA, pH 7,4, 0,2 mM PMSF). </li><li> Starten des Größenausschluss-Chromatographie mit dem Puffer bei einer Flussrate von 0,5 ml / min ausgeführt. </li><li> Sammeln Sie die Fraktionen der gereinigten Mgm101 Gipfeln. Legen Aliquots der Fraktionen auf einem 12% SDS-PAGE zur Überprüfung der Qualität des fertigen Protein. </li><li> Konzentrieren des Proteins mit VIVASPIN 6, dann schnell frieren die Proben in flüssigem N2 und bei -80 ° C </li><li> Verwenden Sie die Mgm101 Proben innerhalb von 6-12 Monaten für ssDNA-Bindungs-Assay (Abbildung 8) und für strukturelle Visualisierung mittels Transmissions-Elektronenmikroskopie (Abbildung 9). </li></ol>

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K., Park, D., Xu, L., Kleckner, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DMC1:+a+meiosis-specific+yeast+homolog+of+E.+coli+recA+required+for+recombination,+synaptonemal+complex+formation,+and+cell+cycle+progression.">DMC1: a meiosis-specific yeast homolog of E. coli recA required for recombination, synaptonemal complex formation, and cell cycle progression.</a> Cell. 69, 439-456 (1992).</li><li>Shinohara, A., Ogawa, H., Ogawa, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rad51+protein+involved+in+repair+and+recombination+in+S.+cerevisiae+is+a+RecA-like+protein.">Rad51 protein involved in repair and recombination in S. cerevisiae is a RecA-like protein.</a> Cell. 69, 457-470 (1992).</li><li>Passy, S. I., 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=Human+Dmc1+protein+binds+DNA+as+an+octameric+ring.">Human Dmc1 protein binds DNA as an octameric ring.</a> Proc. Natl. Acad. Sci. U.S.A. 96, 10684-10688 (1999).</li><li>Story, R. M., Weber, I. T., Steitz, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+structure+of+the+E.+coli+recA+protein+monomer+and+polymer.">The structure of the E. coli recA protein monomer and polymer.</a> Nature. 355, 318-325 (1992).</li><li>Yu, X., Jacobs, S. A., West, S. C., Ogawa, T., Egelman, E. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Domain+structure+and+dynamics+in+the+helical+filaments+formed+by+RecA+and+Rad51+on+DNA.">Domain structure and dynamics in the helical filaments formed by RecA and Rad51 on DNA.</a> Proc. Natl. Acad. Sci. U.S.A. 98, 8419-8424 (2001).</li><li>Conway, A. 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=Crystal+structure+of+a+Rad51+filament.">Crystal structure of a Rad51 filament.</a> Nat. Struct. Mol. Biol. 11, 791-796 (2004).</li><li>Bai, Y., Davis, A. P., Symington, L. S. <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+allele+of+RAD52+that+causes+severe+DNA+repair+and+recombination+deficiencies+only+in+the+absence+of+RAD51+or+RAD59.">A novel allele of RAD52 that causes severe DNA repair and recombination deficiencies only in the absence of RAD51 or RAD59.</a> Genetics. 153, 1117-1130 (1999).</li><li>Bai, Y., Symington, L. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Rad52+homolog+is+required+for+RAD51-independent+mitotic+recombination+in+Saccharomyces+cerevisiae.">A Rad52 homolog is required for RAD51-independent mitotic recombination in Saccharomyces cerevisiae.</a> Genes Dev. 10, 2025-2037 (1996).</li><li>Paques, F., Haber, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiple+pathways+of+recombination+induced+by+double-strand+breaks+in+Saccharomyces+cerevisiae.">Multiple pathways of recombination induced by double-strand breaks in Saccharomyces cerevisiae.</a> Microbiol. Mol. Biol. Rev. 63, 349-404 (1999).</li><li>Lopes, A., Amarir-Bouhram, J., Faure, G., Petit, M. A., Guerois, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+novel+recombinases+in+bacteriophage+genomes+unveils+Rad52,+Rad51+and+Gp2.5+remote+homologs.">Detection of novel recombinases in bacteriophage genomes unveils Rad52, Rad51 and Gp2.5 remote homologs.</a> Nucleic Acids Res. 38, 3952-3962 (2010).</li><li>Poteete, A. R., Sauer, R. T., Hendrix, R. 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U.S.A. 96, 4279-4284 (1999).</li><li>Ploquin, 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=Functional+and+structural+basis+for+a+bacteriophage+homolog+of+human+RAD52.">Functional and structural basis for a bacteriophage homolog of human RAD52.</a> Curr. Biol. 18, 1142-1146 (2008).</li><li>Chen, X. J., Guan, M. X., Clark-Walker, G. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MGM101,+a+nuclear+gene+involved+in+maintenance+of+the+mitochondrial+genome+in+Saccharomyces+cerevisiae.">MGM101, a nuclear gene involved in maintenance of the mitochondrial genome in Saccharomyces cerevisiae.</a> Nucl. Acids Res. 21, 3473-3477 (1993).</li><li>Meeusen, S., 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=Mgm101p+is+a+novel+component+of+the+mitochondrial+nucleoid+that+binds+DNA+and+is+required+for+the+repair+of+oxidatively+damaged+mitochondrial+DNA.">Mgm101p is a novel component of the mitochondrial nucleoid that binds DNA and is required for the repair of oxidatively damaged mitochondrial DNA.</a> J. Cell Biol. 145, 291-304 (1999).</li><li>Mbantenkhu, 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=Mgm101+is+a+Rad52-related+protein+required+for+mitochondrial+DNA+recombination.">Mgm101 is a Rad52-related protein required for mitochondrial DNA recombination.</a> J. Biol. Chem. 286, 42360-42370 (2011).</li><li>Nardozzi, J. D., Wang, X., Mbantenkhu, M., Wilkens, S., Chen, X. 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+properly+configured+ring+structure+is+critical+for+the+function+of+the+mitochondrial+DNA+recombination+protein.">A properly configured ring structure is critical for the function of the mitochondrial DNA recombination protein.</a> Mgm101. J. Biol. Chem. 287, 37259-37268 (2012).</li><li>Zuo, X., Xue, D., Li, N., Clark-Walker, G. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+functional+core+of+the+mitochondrial+genome+maintenance+protein+Mgm101p+in+Saccharomyces+cerevisiae+determined+with+a+temperature-conditional+allele.">A functional core of the mitochondrial genome maintenance protein Mgm101p in Saccharomyces cerevisiae determined with a temperature-conditional allele.</a> FEMS Yeast Res. 7, 131-140 (2007).</li><li>Itoh, K., 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=DNA+packaging+proteins+Glom+and+Glom2+coordinately+organize+the+mitochondrial+nucleoid+of+Physarum+polycephalum.">DNA packaging proteins Glom and Glom2 coordinately organize the mitochondrial nucleoid of Physarum polycephalum.</a> Mitochondrion. 11, 575-586 (2011).</li><li>Janicka, S., 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+RAD52-like+single-stranded+DNA+binding+protein+affects+mitochondrial+DNA+repair+by+recombination.">A RAD52-like single-stranded DNA binding protein affects mitochondrial DNA repair by recombination.</a> Plant J. 72, 423-435 (2012).</li></ol>

Die Autoren erklären, dass sie keine finanziellen Interessen haben.

Es war eine Herausforderung, um eine stabile, nativen rekombinanten Protein aus E. Mgm101 produzieren coli möglicherweise aufgrund seiner Unlöslichkeit in Bakterienzellen. In diesem Bericht zeigen wir, dass die MBP-Fusion-Strategie das Protein zu einem angemessen hohen Niveau exprimiert werden können. Durch negative Färbung Transmissionselektronenmikroskopie und Größenausschlusschromatographie, haben wir bereits gezeigt, dass die MBP-Fusionsprotein einheitliche Oligomere bildet in vitro ...

Homologe Rekombination ist für die Reparatur von Doppelstrangbrüchen (DSB) und Interstrang Vernetzungen und für die Wiederaufnahme der DNA-Replikation von eingestürzten Replikationsgabeln 1 wichtig. In konventionellen homologen Rekombination ist die zentrale Reaktion der ATP-abhängigen Rekombinasen wie RecA in Prokaryoten und Rad51 und Dmc1 in Eukaryonten 1-3 katalysiert wird. Diese Rekombinase bilden nucleoprotein Filamente auf ssDNA, die unerlässlich für die Einleitung Homologiesuche und Stranginvasion innerhalb duplex DNA-Templates (Abbildung 1, links) 4-7 sind. Zusätzlich zu den herkömmlichen Schema kann homologe Rekombination auch in einer Weise RecA/Rad51-independent (Abbildung 1, rechts). Zum Beispiel kann die Hefe Rad52 und Rad59 Proteine ​​direkt katalysieren die Anlagerung komplementäre ssDNA-Stränge, die durch Resektion von dsDNA Unterbrechungen ausgesetzt sind. Diese Rekombination Prozess, da singen bekanntle Banddurchlaufanlagen, hat in der Regel nicht um homologe Paarung mit dsDNA Vorlagen. Nach dem Glühen werden heterologe Schwänze durch Exonucleasen entfernt und Kerben sind ligiert Genom Kontinuität 8-10 wiederherzustellen. Reparatur durch den einzigen Banddurchlaufanlagen Mechanismus wird oft durch Deletionen von genomischen Sequenzen zwischen direkt wiederholt Regionen begleitet. Rad52 gehört zu einer vielfältigen Gruppe von Proteinen, die Rekombination verbreitet unter 11 Bakteriophagen sind. Diese Proteine ​​sind auch als Single Strand Annealing Proteine ​​(SSAPs) bekannt, auf der Grundlage ihrer Aktivität in der Förderung der Anlagerung homologen einzelsträngige DNA-Moleküle. Die am besten charakterisierten Bakteriophagen SSAPs sind Redβ und Erf vom Bakteriophagen λ und P22, RecT vom Prophagen rac und der Sak-Protein aus der Lactococcus-Phagen UL36. Die SSAPs sind strukturell durch eine typische β-β-β-α fach dadurch, obwohl Ähnlichkeit praktisch Nichterfassungssignal wirdkönnen in ihrer primären Sequenzen. Sie alle bilden große homooligomeren Ringe von 10 - 14 fache Symmetrie in vitro 12-14. Die funktionellen Auswirkungen dieser Eigenschaft höherer Ordnung strukturelle Organisation ist nicht gut verstanden. Wir sind daran interessiert, zu verstehen, den Mechanismus der homologen Rekombination in der mitochondrialen Genoms. Wir haben zuvor die MGM101 Gen, das für die Aufrechterhaltung der mtDNA in Saccharomyces cerevisiae 15 identifiziert. MGM101 anschließend wurde festgestellt, dass mitochondriale Nukleoide an und ist für die Toleranz der mtDNA auf DNA-schädigende Mittel 16 erforderlich. Allerdings wurde in der Studie von Mgm101 wurde zurück in den letzten zehn Jahren durch die Schwierigkeit gehalten rekombinanten Mgm101 erzeugen. Wir haben vor kurzem in der Herstellung von löslichen Mgm101 bei großen Mengen aus E. gelungen coli mit dem MBP-Fusion-Strategie. Dies hat es uns ermöglicht, dass Mgm101 Aktien demonstrierenbiochemische und strukturelle Ähnlichkeiten mit dem Rad52-Familie von Proteinen 17,18. In diesem Bericht wird eine dreistufige Reinigungsverfahren beschrieben, die produziert homogene Mgm101for biochemische und strukturelle Analysen (Abbildung 2).

<table border="1" fo:keep-together.within-page="always">
	<tbody>
		<tr>
			<td>Name of Reagent/Material</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Expression vector pMAL-c2E</td>
			<td>New England Biolabs</td>
			<td>#N8066S</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>PreScission Protease</td>
			<td>GE Healthcare Life Sciences</td>
			<td>#27-0843-01</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>BL21-CodonPlus(DE3)-RIL cells</td>
			<td>Strategene</td>
			<td>#230245</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Leupeptin</td>
			<td>Roche Applied Science</td>
			<td>#11034626001</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Pepstatin</td>
			<td>Roche Applied Science</td>
			<td>#11359053001</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Phenylmethylsulfonyl fluoride (PMSF)</td>
			<td>Roche Applied Science</td>
			<td>#10837091001</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>DNAse I</td>
			<td>Sigma</td>
			<td>#DN25-1G</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Isopropyl &beta;-D-1-thiogalactopyranoside (IPTG)</td>
			<td>Roche Applied Science</td>
			<td>#11411446001</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Amylose resin</td>
			<td>New England Biolabs</td>
			<td>#E8021L</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Econo-Column chromatography column</td>
			<td>BIO-RAD</td>
			<td>#7372512</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Bio-Scale Mini Macro-Prep High S cartridge (1 ml)</td>
			<td>BIO-RAD</td>
			<td>#732-4130</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>VIVASPIN 15R Ultrafiltration spin column (10,000 MWCO)</td>
			<td>Sartorius Stedium</td>
			<td>#VS15RH02</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Superose 6 prep grade column</td>
			<td>Amersham Bioscirnces</td>
			<td>#17-0489-01</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>VIVASPIN 6 Ultrafiltration spin column (5,000 MWCO)</td>
			<td>Sartorius Stedium</td>
			<td>#VS0611</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

preparation of the mgm101 recombination protein by mbp-based tagging strategy

Die MGM101 Gen wurde vor 20 Jahren für seine Rolle bei der Aufrechterhaltung der mitochondrialen DNA identifiziert. Studien aus mehreren Gruppen haben vorgeschlagen, dass das Protein in der Mgm101 recombinational Reparatur der mitochondrialen DNA beteiligt ist. Neuere Untersuchungen haben gezeigt, dass Mgm101 der Rad52-Typ Rekombinationsprotein Familie verwandt ist. Diese Proteine ​​bilden große oligomere Ringe und fördern die Anlagerung homologen einzelne DNA-Moleküle. Allerdings hat die Charakterisierung von Mgm101 der Schwierigkeit bei der Herstellung des rekombinanten Proteins behindert. Hier wird ein zuverlässiges Verfahren zur Herstellung von rekombinantem Mgm101 beschrieben. Maltose Binding Protein (MBP)-markierten Mgm101 zunächst in Escherichia coli exprimiert. Das Fusionsprotein wird zunächst durch Amylose-Affinitätschromatographie gereinigt. Nach der Begrüßung durch proteolytische Spaltung freigesetzt wird Mgm101 von MBP durch Kationenaustauschchromatographieschritt getrennt. Monodispersen Mgm101 erhält danndurch Größenausschlusschromatographie. Eine Ausbeute von ~ 0,87 mg Mgm101 pro Liter Bakterienkultur kann routinemäßig erhalten. Das rekombinante Mgm101 eine minimale Verunreinigung der DNA. Die vorbereiteten Proben werden erfolgreich für biochemische, strukturelle und Single Particle-Image-Analysen von Mgm101 verwendet. Dieses Protokoll kann auch zur Herstellung von anderen großen oligomere DNA-bindende Proteine ​​falsch gefaltet und giftig für Bakterienzellen verwendet werden.

Mgm101 ist ein Rad52-bezogenen Rekombinationsprotein in Mitochondrien. Rad52 wurde ausgiebig für seine Rolle in der mitochondrialen DNA-Rekombination (Abbildung 1) untersucht. Rekombinante Mgm101 kann durch eine Drei-Schritt-Verfahren (Abbildung 2) hergestellt werden. Dies wird durch die Verwendung des MBP-Tagging Strategie Mgm101 in eine lösliche Form exprimiert werden und anschließend von dem Tag durch proteolytische Spaltung freigesetzt (Fig. 3) kann erleichtert. ...

Watch this Scientific Journal Video about Preparation of the Mgm101 Recombination Protein by MBP-based Tagging Strategy at JoVE.com

Preparation of the Mgm101 Recombination Protein by MBP-based Tagging Strategy

Die Hefe-Mitochondrien nucleoid Protein, Mgm101, ist ein Rad52-Typ Rekombinationsprotein die große oligomere Ringe bildet. Ein Protokoll wird beschrieben, dass lösliches rekombinantes Mgm101 vorzubereiten mit dem Maltose Binding Protein (MBP)-Tagging-Strategie mit Kationenaustausch und Größenausschlusschromatographie gekoppelt.

Vorbereitung des Mgm101 Rekombinationsprotein von MBP-based Tagging-Strategie

The MGM101 gene was identified 20 years ago for its role in the maintenance of mitochondrial DNA. Studies from several groups have suggested that the ...

preparation-mgm101-recombination-protein-mbp-based-tagging

Research

JoVE Journal

Biology

12.0K Aufrufe.  State University of New York Upstate Medical University. Die Hefe-Mitochondrien nucleoid Protein, Mgm101, ist ein Rad52-Typ Rekombinationsprotein die große oligomere Ringe bildet. Ein Protokoll wird beschrieben, dass lösliches rekombinantes Mgm101 vorzubereiten mit dem Maltose Binding Protein (MBP)-Tagging-Strategie mit Kationenaustausch und Größenausschlusschromatographie gekoppelt.

Serie: Preparation of the Mgm101 Recombination Protein by MBP-based Tagging Strategy

Staining of Proteins in Gels with Coomassie G-250 without Organic Solvent and Acetic Acid

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents (Methanol, Ethanol or 2-Propanol) and acetic acid are used for fixation, staining and destaining of proteins in a gel after SDS-PAGE. To speed up the procedure, heating the staining solution in the microwave oven for a short time is frequently used. This usually results in evaporation of toxic or hazardous Methanol, Ethanol or 2-Propanol and a strong smell of acetic acid in the lab which should be avoided due to safety considerations. In a protocol originally published in two patent applications by E.M. Wondrak (US2001046709 (A1), US6319720 (B1)), an alternative composition of the staining solution is described in which no organic solvent or acid is used. The CBB is dissolved in bidistilled water (60-80mg of CBB G-250 per liter) and 35 mM HCl is added as the only other compound in the staining solution. The CBB staning of the gel is done after SDS-PAGE and thorough washing of the gel in bidistilled water. By heating the gel during the washing and staining steps, the process can be finished faster and no toxic or hazardous compunds are evaporating. The staining of proteins occurs already within 1 minute after heating the gel in staining solution and is fully developed after 15-30 min with a slightly blue background that is destained completely by prolonged washing of the stained gel in bidistilled water, without affecting the stained protein bands.

A short protocol for protein staining with Coomassie Brilliant Blue (CBB) G-250 in polyacrylamide gels is described without using organic solvents or acetic acid as in the classical staining procedures with CBB.

Färbung von Proteinen in Gelen mit Coomassie G-250 ohne organische Lösungsmittel und Essigsäure

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents ...

Forschung

Biologie

Using the GELFREE 8100 Fractionation System for Molecular Weight-Based Fractionation with Liquid Phase Recovery

The GELFREE 8100 Fractionation System is a novel protein fractionation system designed to maximize protein recovery during molecular weight based fractionation. The system is comprised of single-use, 8-sample capacity cartridges and a benchtop GELFREE Fractionation Instrument. During separation, a constant voltage is applied between the anode and cathode reservoirs, and each protein mixture is electrophoretically driven from a loading chamber into a specially designed gel column gel. Proteins are concentrated into a tight band in a stacking gel, and separated based on their respective electrophoretic mobilities in a resolving gel. As proteins elute from the column, they are trapped and concentrated in liquid phase in the collection chamber, free of the gel. The instrument is then paused at specific time intervals, and fractions are collected using a pipette. This process is repeated until all desired fractions have been collected. If fewer than 8 samples are run on a cartridge, any unused chambers can be used in subsequent separations.
This novel technology facilitates the quick and simple separation of up to 8 complex protein mixtures simultaneously, and offers several advantages when compared to previously available fractionation methods. This system is capable of fractionating up to 1mg of total protein per channel, for a total of 8mg per cartridge. Intact proteins over a broad mass range are separated on the basis of molecular weight, retaining important physiochemical properties of the analyte. The liquid phase entrapment provides for high recovery while eliminating the need for band or spot cutting, making the fractionation process highly reproducible1.

The accompanying video describes the use of the GELFREE 8100 Fractionation System, which partitions complex protein samples on the basis of molecular weight and recovers the fractions in liquid phase. The video describes how the technology works, how it is used, and provides resultant data, with polyacrylamide gel electrophoresis analysis of fractionated bovine liver homogenate.

Mit dem GELFREE 8100 Fraktionierung System für Molecular Weight-Based Fraktionierung mit Liquid Phase Wiederherstellung

The GELFREE 8100 Fractionation System is a novel protein fractionation system designed to maximize protein recovery during molecular weight based ...

Identifying the Effects of BRCA1 Mutations on Homologous Recombination using Cells that Express Endogenous Wild-type BRCA1

The functional analysis of missense mutations can be complicated by the presence in the cell of the endogenous protein. Structure-function analyses of the BRCA1 have been complicated by the lack of a robust assay for the full length BRCA1 protein and the difficulties inherent in working with cell lines that express hypomorphic BRCA1 protein1,2,3,4,5. We developed a system whereby the endogenous BRCA1 protein in a cell was acutely depleted by RNAi targeting the 3'-UTR of the BRCA1 mRNA and replaced by co-transfecting a plasmid expressing a BRCA1 variant. One advantage of this procedure is that the acute silencing of BRCA1 and simultaneous replacement allow the cells to grow without secondary mutations or adaptations that might arise over time to compensate for the loss of BRCA1 function. This depletion and add-back procedure was done in a HeLa-derived cell line that was readily assayed for homologous recombination activity. The homologous recombination assay is based on a previously published method whereby a recombination substrate is integrated into the genome (Figure 1)6,7,8,9. This recombination substrate has the rare-cutting I-SceI restriction enzyme site inside an inactive GFP allele, and downstream is a second inactive GFP allele. Transfection of the plasmid that expresses I-SceI results in a double-stranded break, which may be repaired by homologous recombination, and if homologous recombination does repair the break it creates an active GFP allele that is readily scored by flow cytometry for GFP protein expression. Depletion of endogenous BRCA1 resulted in an 8-10-fold reduction in homologous recombination activity, and add-back of wild-type plasmid fully restored homologous recombination function. When specific point mutants of full length BRCA1 were expressed from co-transfected plasmids, the effect of the specific missense mutant could be scored. As an example, the expression of the BRCA1(M18T) protein, a variant of unknown clinical significance10, was expressed in these cells, it failed to restore BRCA1-dependent homologous recombination. By contrast, expression of another variant, also of unknown significance, BRCA1(I21V) fully restored BRCA1-dependent homologous recombination function. This strategy of testing the function of BRCA1 missense mutations has been applied to another biological system assaying for centrosome function (Kais et al, unpublished observations). Overall, this approach is suitable for the analysis of missense mutants in any gene that must be analyzed recessively.

We provide a method for testing BRCA1 variants in a tissue culture based assay for homologous recombination repair of DNA damage by depleting endogenous BRCA1 protein from a cell using RNAi and replacing it with a BRCA1 point mutant that contains a coding change.

Ermittlung der Auswirkungen von BRCA1-Mutationen auf homologe Rekombination unter Verwendung von Zellen, die endogenes Wildtyp-BRCA1 Express

The functional analysis of missense mutations can be complicated by the presence in the cell of the endogenous protein. Structure-function analyses of the ...

Genetic Modification and Recombination of Salivary Gland Organ Cultures

Branching morphogenesis occurs during the development of many organs, and the embryonic mouse submandibular gland (SMG) is a classical model for the study of branching morphogenesis. In the developing SMG, this process involves iterative steps of epithelial bud and duct formation, to ultimately give rise to a complex branched network of acini and ducts, which serve to produce and modify/transport the saliva, respectively, into the oral cavity1-3. The epithelial-associated basement membrane and aspects of the mesenchymal compartment, including the mesenchyme cells, growth factors and the extracellular matrix, produced by these cells, are critical to the branching mechanism, although how the cellular and molecular events are coordinated remains poorly understood 4. The study of the molecular mechanisms driving epithelial morphogenesis advances our understanding of developmental mechanisms and provides insight into possible regenerative medicine approaches. Such studies have been hampered due to the lack of effective methods for genetic manipulation of the salivary epithelium. Currently, adenoviral transduction represents the most effective method for targeting epithelial cells in adult glands in vivo5. However, in embryonic explants, dense mesenchyme and the basement membrane surrounding the epithelial cells impedes viral access to the epithelial cells. If the mesenchyme is removed, the epithelium can be transfected using adenoviruses, and epithelial rudiments can resume branching morphogenesis in the presence of Matrigel or laminin-1116,7. Mesenchyme-free epithelial rudiment growth also requires additional supplementation with soluble growth factors and does not fully recapitulate branching morphogenesis as it occurs in intact glands8. Here we describe a technique which facilitates adenoviral transduction of epithelial cells and culture of the transfected epithelium with associated mesenchyme. Following microdissection of the embryonic SMGs, removal of the mesenchyme, and viral infection of the epithelium with a GFP-containing adenovirus, we show that the epithelium spontaneously recombines with uninfected mesenchyme, recapitulating intact SMG glandular structure and branching morphogenesis. The genetically modified epithelial cell population can be easily monitored using standard fluorescence microscopy methods, if fluorescently-tagged adenoviral constructs are used. The tissue recombination method described here is currently the most effective and accessible method for transfection of epithelial cells with a wild-type or mutant vector within a complex 3D tissue construct that does not require generation of transgenic animals.

A technique to genetically manipulate epithelial cells within whole ex vivo cultured embryonic mouse submandibular glands (SMGs) using viral gene transfer is described. This method takes advantage of the innate ability of SMG epithelium and mesenchyme to spontaneously recombine after separation and infection of epithelial rudiments with adenoviral vectors.

Genetic Modification und Rekombination von Speicheldrüsen Organkulturen

Branching  morphogenesis occurs during the development of many organs, and the embryonic  mouse submandibular gland (SMG) is a classical model for the ...

Recombineering Homologous Recombination Constructs in Drosophila

The continued development of techniques for fast, large-scale manipulation of endogenous gene loci will broaden the use of Drosophila melanogaster as a genetic model organism for human-disease related research. Recent years have seen technical advancements like homologous recombination and recombineering. However, generating unequivocal null mutations or tagging endogenous proteins remains a substantial effort for most genes. Here, we describe and demonstrate techniques for using recombineering-based cloning methods to generate vectors that can be used to target and manipulate endogenous loci in vivo. Specifically, we have established a combination of three technologies: (1) BAC transgenesis/recombineering, (2) ends-out homologous recombination and (3) Gateway technology to provide a robust, efficient and flexible method for manipulating endogenous genomic loci. In this protocol, we provide step-by-step details about how to (1) design individual vectors, (2) how to clone large fragments of genomic DNA into the homologous recombination vector using gap repair, and (3) how to replace or tag genes of interest within these vectors using a second round of recombineering. Finally, we will also provide a protocol for how to mobilize these cassettes in vivo to generate a knockout, or a tagged gene via knock-in. These methods can easily be adopted for multiple targets in parallel and provide a means for manipulating the Drosophila genome in a timely and efficient manner.

Recombineering Homologous Recombination Constructs in Drosophila

Homologous recombination techniques greatly advance Drosophila genetics by enabling the creation of molecularly precise mutations. The recent adoption of recombineering allows one to manipulate large pieces of DNA and transform them into Drosophila6. The methods presented here combine these techniques to rapidly generate large homologous recombination vectors.

Recombineering homologen Rekombination Konstrukte in<em&gt; Drosophila</em

The continued development of techniques for fast, large-scale manipulation of endogenous gene loci will broaden the use of Drosophila melanogaster as a ...

Improving the Success Rate of Protein Crystallization by Random Microseed Matrix Screening

Random microseed matrix screening (rMMS) is a protein crystallization technique in which seed crystals are added to random screens. By increasing the likelihood that crystals will grow in the metastable zone of a protein's phase diagram, extra crystallization leads are often obtained, the quality of crystals produced may be increased, and a good supply of crystals for data collection and soaking experiments is provided. Here we describe a general method for rMMS that may be applied to either sitting drop or hanging drop vapor diffusion experiments, established either by hand or using liquid handling robotics, in 96-well or 24-well tray format.

Here we describe a general method for random microseed matrix screening. This technique is shown to significantly increase the success rate of protein crystallization screening experiments, reduce the need for optimization, and provide a reliable supply of crystals for data collection and ligand-soaking experiments.

Verbesserung der Erfolgsrate der Proteinkristallisation nach Zufall Microseed Matrix Screening

Random microseed matrix screening  (rMMS) is a protein crystallization technique in which seed crystals are added  to random screens. By increasing the ...

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

The production of recombinant membrane proteins for structural and functional studies remains technically challenging due to low levels of expression and the inherent instability of many membrane proteins once solubilized in detergents. A protocol is described that combines ligation independent cloning of membrane proteins as GFP fusions with expression in Escherichia coli detected by GFP fluorescence. This enables the construction and expression screening of multiple membrane protein/variants to identify candidates suitable for further investment of time and effort. The GFP reporter is used in a primary screen of expression by visualizing GFP fluorescence following SDS polyacrylamide gel electrophoresis (SDS-PAGE). Membrane proteins that show both a high expression level with minimum degradation as indicated by the absence of free GFP, are selected for a secondary screen. These constructs are scaled and a total membrane fraction prepared and solubilized in four different detergents. Following ultracentrifugation to remove detergent-insoluble material, lysates are analyzed by fluorescence detection size exclusion chromatography (FSEC). Monitoring the size exclusion profile by GFP fluorescence provides information about the mono-dispersity and integrity of the membrane proteins in different detergents. Protein: detergent combinations that elute with a symmetrical peak with little or no free GFP and minimum aggregation are candidates for subsequent purification. Using the above methodology, the heterologous expression in E. coli of SED (shape, elongation, division, and sporulation) proteins from 47 different species of bacteria was analyzed. These proteins typically have ten transmembrane domains and are essential for cell division. The results show that the production of the SEDs orthologues in E. coli was highly variable with respect to the expression levels and integrity of the GFP fusion proteins. The experiment identified a subset for further investigation.

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

A streamlined approach to screening for the expression of recombinant membrane proteins in Escherichia coli based on fusion to green fluorescent protein is presented.

Green Fluorescent Protein-basierte Screening Expression von Membranproteinen in<em&gt; Escherichia coli</em

The production of recombinant membrane proteins for structural and functional studies remains technically challenging due to low levels of expression and ...

Detecting Protein Subcellular Localization by Green Fluorescence Protein Tagging and 4',6-Diamidino-2-phenylindole Staining in Caenorhabditis elegans

In this protocol, a green fluorescence protein (GFP) fusion protein and 4',6-diamidino-2-phenylindole (DAPI) staining are used to track protein subcellular localization changes; in particular, a nuclear translocation under a heat stress condition. Proteins react correspondingly to external and internal signals. A common mechanism is to change its subcellular localization. This article describes a protocol to track protein localization that does not require an antibody, radioactive labeling, or a confocal microscope. In this article, GFP is used to tag the target protein EXL-1 in C. elegans, a member of the chloride intracellular channel proteins (CLICs) family, including mammalian CLIC4. An integrated translational exl-1::gfp transgenic line (with a promoter and a full gene sequence) was created by transformation and &#947;-radiation, and stably expresses the gene and gfp. Recent research showed that upon heat stress, not oxidative stress, EXL-1::GFP accumulates in the nucleus. Overlapping the GFP signal with both the nuclei structure and the DAPI signals confirms the EXL-1 subcellular localization changes under stress. This protocol presents two different fixation methods for DAPI staining: ethanol fixation and acetone fixation. The DAPI staining protocol presented in this article is fast and efficient and preserves both the GFP signal and the protein subcellular localization changes. This method only requires a fluorescence microscope with Nomarski, a FITC filter, and a DAPI filter. It is suitable for a small laboratory setting, undergraduate student research, high school student research, and biotechnology classrooms.

Detecting Protein Subcellular Localization by Green Fluorescence Protein Tagging and 4&#039;,6-Diamidino-2-phenylindole Staining in Caenorhabditis elegans

This protocol demonstrates how to track a protein nuclear translocation under heat stress by using a green fluorescence protein (GFP) fusion protein as a marker and 4',6-diamidino-2-phenylindole (DAPI) staining. The DAPI staining protocol is fast and preserves the GFP and protein subcellular localization signals.

Erkennung von Protein subzelluläre Lokalisation durch grüne Fluoreszenz Protein Tagging und 4', 6-Diamidino-2-Phenylindole Färbung in Caenorhabditis elegans

In this protocol, a green fluorescence protein (GFP) fusion protein and 4',6-diamidino-2-phenylindole (DAPI) staining are used to track protein ...

Detecting and Characterizing Protein Self-Assembly In Vivo by Flow Cytometry

Protein self-assembly governs protein function and compartmentalizes cellular processes in space and time. Current methods to study it suffer from low-sensitivity, indirect read-outs, limited throughput, and/or population-level rather than single-cell resolution. We designed a flow cytometry-based single methodology that addresses all of these limitations: Distributed Amphifluoric FRET or DAmFRET. DAmFRET detects and quantifies protein self-assemblies by sensitized emission FRET in vivo, enables deployment across model systems-from yeast to human cells-and achieves sensitive, single-cell, high-throughput read-outs irrespective of protein localization or solubility.

This article describes a FRET-based flow cytometry protocol to quantify protein self-assembly in both S. cerevisiae and HEK293T cells.

Erkennung und Charakterisierung der Protein-Selbstmontage in Vivo durch Durchflusszytometrie

Protein self-assembly governs protein function and compartmentalizes cellular processes in space and time. Current methods to study it suffer from ...

An Improved Chemotaxis Assay for the Rapid Identification of Rhizobacterial Chemoattractants in Root Exudates

Chemotaxis identification is very important for the research and application of rhizosphere growth-promoting bacteria. We established a straightforward method to quickly identify the chemoattractants that could induce the chemotactic movement of rhizosphere growth-promoting bacteria on sterile glass slides via simple steps. Bacteria solution (OD600 = 0.5) and sterile chemoattractant aqueous solution were added dropwise on the glass slide at an interval of 1 cm. An inoculating loop was used to connect the chemoattractant aqueous solution to the bacterial solution. The slide was kept at room temperature for 20 min on the clean bench. Finally, the chemoattractant aqueous solution was collected for bacterial counting and microscopic observation. In this study, through multiple comparisons of experimental results, the method overcame multiple shortcomings of traditional bacterial chemotaxis methods. The method reduced the error of plate counting and shortened the experimental cycle. For the identification of chemoattractant substances, this new method can save 2-3 days compared to the traditional method. Additionally, this method allows any researcher to systematically complete a bacterial chemotaxis experiment within 1-2 days. The protocol can be considered a valuable resource for understanding plant-microbe interactions.

Here, we present an improved chemotaxis assay protocol. The goal of this protocol is to reduce the steps and costs of traditional bacterial chemotaxis methods and to serve as a valuable resource for understanding plant-microbe interactions.

Ein verbesserter Chemotaxis-Assay zur schnellen Identifizierung von rhizobakteriellen Chemoattraktantien in Wurzelexsudaten

Chemotaxis identification is very important for the research and application of rhizosphere growth-promoting bacteria. We established a straightforward ...