Agradecemos Olivier Vallon para o anti-soro contra CF1β. Este trabalho foi financiado pela Sociedade Max Planck e bolsas da Deutsche Forschungsgemeinschaft (Schr 617/5-1) eo Bundesministerium für Bildung und Forschung (Forsys Biologia de Sistemas, GoFORSYS iniciativa do projeto).

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	<li>Perrakis, A., Musacchio, A., Cusack, S., Petosa, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigating+a+macromolecular+complex:+the+toolkit+of+methods.">Investigating a macromolecular complex: the toolkit of methods.</a> J. Struct. Biol. 175, 106-112 (2011).</li><li>Gavin, A. C., Maeda, K., Kuhner, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+charting+protein-protein+interaction:+mass+spectrometry-based+approaches.">Recent advances in charting protein-protein interaction: mass spectrometry-based approaches.</a> Curr. Opin. Biotechnol. 22, 42-49 (2011).</li><li>Markham, K., Bai, Y., Schmitt-Ulms, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Co-immunoprecipitations+revisited:+an+update+on+experimental+concepts+and+their+implementation+for+sensitive+interactome+investigations+of+endogenous+proteins.">Co-immunoprecipitations revisited: an update on experimental concepts and their implementation for sensitive interactome investigations of endogenous proteins.</a> Anal. Bioanal. Chem. 389, 461-473 (2007).</li><li>Selbach, M., 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=Protein+interaction+screening+by+quantitative+immunoprecipitation+combined+with+knockdown+(QUICK.">Protein interaction screening by quantitative immunoprecipitation combined with knockdown (QUICK.</a> Nat Methods. 3, 981-983 (2006).</li><li>Ong, S. E., 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=A+practical+recipe+for+stable+isotope+labeling+by+amino+acids+in+cell+culture+(SILAC).">A practical recipe for stable isotope labeling by amino acids in cell culture (SILAC).</a> Nat Protoc. 1, 2650-2660 (2006).</li><li>Heide, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+quantitative+immunoprecipitation+combined+with+knockdown+and+cross-linking+to+Chlamydomonas+reveals+the+presence+of+vesicle-inducing+protein+in+plastids+1+in+a+common+complex+with+chloroplast+HSP90C.">Application of quantitative immunoprecipitation combined with knockdown and cross-linking to Chlamydomonas reveals the presence of vesicle-inducing protein in plastids 1 in a common complex with chloroplast HSP90C.</a> Proteomics. 9, 3079-3089 (2009).</li><li>Nordhues, A., Miller, S. M., Muhlhaus, T., Schroda, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+insights+into+the+roles+of+molecular+chaperones+in+Chlamydomonas+and+Volvox.">New insights into the roles of molecular chaperones in Chlamydomonas and Volvox.</a> International review of cell and molecular biology. 285, 75-113 (2010).</li><li>Mayer, M. P., Bukau, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hsp70+chaperones:+cellular+functions+and+molecular+mechanism.">Hsp70 chaperones: cellular functions and molecular mechanism.</a> Cell Mol. Life Sci. 62, 670-684 (2005).</li><li>Schroda, M., Vallon, O., Whitelegge, J. P., Beck, C. F., Wollman, F. 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+chloroplastic+GrpE+homolog+of+Chlamydomonas:+two+isoforms+generated+by+differential+splicing.">The chloroplastic GrpE homolog of Chlamydomonas: two isoforms generated by differential splicing.</a> The Plant Cell. 13, 2823-2839 (2001).</li><li>Willmund, F., Schroda, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HEAT+SHOCK+PROTEIN+90C+is+a+bona+fide+Hsp90+that+interacts+with+plastidic+HSP70B+in+Chlamydomonas+reinhardtii.">HEAT SHOCK PROTEIN 90C is a bona fide Hsp90 that interacts with plastidic HSP70B in Chlamydomonas reinhardtii.</a> Plant Physiol. 138, 2310-2322 (2005).</li><li>Harris, 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=.">.</a> The Chlamydomonas Sourcebook: Introduction to Chlamydomonas and Its Laboratory Use. , (2008).</li><li>Mortensen, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MSQuant,+an+open+source+platform+for+mass+spectrometry-based+quantitative+proteomics.">MSQuant, an open source platform for mass spectrometry-based quantitative proteomics.</a> J. Proteome Res. 9, 393-403 (2010).</li><li>M?hlhaus, T., Weiss, J., Hemme, D., Sommer, F., Schroda, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+Shotgun+Proteomics+Using+a+Uniform+15N-Labeled+Standard+to+Monitor+Proteome+Dynamics+in+Time+Course+Experiments+Reveals+New+Insights+into+the+Heat+Stress+Response+of+Chlamydomonas+reinhardtii.">Quantitative Shotgun Proteomics Using a Uniform 15N-Labeled Standard to Monitor Proteome Dynamics in Time Course Experiments Reveals New Insights into the Heat Stress Response of Chlamydomonas reinhardtii.</a> Mol. Cell Proteomics. 10, (2011).</li><li>Bukau, B., Horwich, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Hsp70+and+Hsp60+chaperone+machines.">The Hsp70 and Hsp60 chaperone machines.</a> Cell. 92, 351-366 (1998).</li><li>Wandinger, S. 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Introduzimos recentemente duas melhorias para a abordagem rápida: um passo para a captura de reticulação transitórios interações proteína-proteína (Quick-X), e uma precipitação de controle para normalizar a eficiência de precipitação desiguais 6. Aqui apresentamos um protocolo contendo duas melhorias mais de RÁPIDO: primeiro, substituir SILAC 5 para 15 N marcação metabólica. As vantagens são que 15 N marcação metabólica é muito mais barato do que SILAC, se 15 N é fornecida como sal inorgânico simples. Além disso, com 15 N metabólica rotulagem QUICK pode ser aplicado a prototrófica organismos para todos os aminoácidos, como a maioria das plantas, fungos e bactérias. E, finalmente, a arginina-prolina interconversão inerente ao SILAC 5,6 não apresenta um problema para a quantificação de 15 N rotulado peptídeos. Exemplos de instrumentos adequados para a avaliação quantitativa da proteômica 15 N são dados 12 MSQUANT ou euOMIQS 13. Em segundo lugar, introduz-se a afinidade de modulação como um meio para reduzir especificamente a quantidade de proteínas que interagem com uma proteína alvo em uma amostra dada em relação a outro. As vantagens desta abordagem são que contorna a construção de mutantes de knockdown, que para alguns sistemas modelo são difíceis de gerar ou não pode ser gerada em tudo, no caso de proteínas-alvo essenciais. Além disso, evita-se interpretações causadas pela expressão diferencial de proteínas potencialmente ocorrer como uma resposta da célula a bater para baixo uma proteína alvo: se outras proteínas são reprimidos bem e reagem de forma cruzada com o anti-soro utilizado para a imunoprecipitação, que seria interpretada como parceiros de interacção verdadeiros da proteína alvo. Por fim, a afinidade de modulação elimina a necessidade de se encontrar uma proporção de anticorpo para o antigénio-apropriada. Apesar de aplicar o nosso protocolo para Chlamydomonas reinhardtii como organismo modelo, Ele pode ser facilmente adaptado a qualquer outro organismo que pode ser cultivada em cultura de células e é capaz de utilizar de amónio ou nitrato como fonte de azoto. Afinidade modulação de complexos de proteínas por ATP / ADP pode ser directamente aplicada a outros chaperones cuja interacção com substratos e proteínas coorte depende do estado de ATP, tal como os sistemas de HSP90 GroEL/HSP60/Cpn60 ou chaperones 14,15, ou a qualquer outro sistema em que afinidades de ligação são modulados por ATP. Afinidade modulação deve funcionar também para os casos em que as afinidades entre interacções proteicas são alterados por drogas específicas, como radicicol geldanamicina ou, no caso de sistemas de Hsp90 15. Uma limitação clara do nosso protocolo é que ele requer purificados por afinidade de anticorpos contra uma proteína alvo conhecida para ser sensíveis a um tratamento específico / droga que modula a sua afinidade para as proteínas parceiras. Portanto, há um método de alto rendimento.

<table border="1"><tbody><tr><td> Nome do reagente </td><td> Companhia </td><td> Número de catálogo </td><td> Comentários (opcional) </td></tr><tr><td> Proteína Sepharose </td><td> Sigma-Aldrich </td><td> P3391 </td><td></td></tr><tr><td> DMP (Dimetil pimelimidate) </td><td> Sigma-Aldrich </td><td> D8388 </td><td> Armazenar dessecado a -20 ° C, dissolvem-se directamente antes da utilização </td></tr><tr><td> Inibidor da protease (completo, EDTA-free) </td><td> Roche Applied Science </td><td> 11873580001 </td><td></td></tr><tr><td> ATP (adenosina-5&#39;-triphosphat) </td><td> Carl Roth </td><td> K054 </td><td></td></tr><tr><td> O fosfato de creatina </td><td> Sigma-Aldrich </td><td> 27920 </td><td></td></tr><tr><td> Creatinafosfoquinase </td><td> Sigma-Aldrich </td><td> C7886 </td><td>; </td></tr><tr><td> DSP Ditiobis [succinimidil propionato] </td><td> Thermo Sientific </td><td> 22585 </td><td> Armazenar dessecado a 4 ° C </td></tr><tr><td> 15 NH 4 Cl </td><td> Cambridge Isotope Laboratories, Andover, MA </td><td> NLM-467 </td><td></td></tr><tr><td> Lys-C (endoproteinase Lys-C) </td><td> Roche Applied Science </td><td> 11047825001 </td><td></td></tr><tr><td> Esferas de tripsina (tripsina imobilizada Poroszyme) </td><td> Applied Biosystems </td><td> 2-3127-00 </td><td> Misture vigorosamente diretamente antes de usar </td></tr><tr><td> Empore Disk mm C 18 47 </td><td> Varian </td><td> 12145004 </td><td></td></tr></tbody></table>

a protocol for the identification of protein-protein interactions based on 15n metabolic labeling, immunoprecipitation, quantitative mass spectrometry and affinity modulation

Interacções proteína-proteína são fundamentais para muitos processos biológicos na célula. Portanto, a sua caracterização desempenha um papel importante na investigação actual e de uma pletora de métodos para a sua investigação é disponível 1. Interacções proteína-proteína são muitas vezes altamente dinâmico e pode depender da localização subcelular, modificações pós-tradução da proteína e do ambiente local 2. Por isso, devem ser investigados no seu ambiente natural, para a qual co-imunoprecipitação abordagens são o método de escolha 3. Parceiros de co-precipitados de interacção são identificados quer por imunotransferência em uma abordagem orientada, ou por espectrometria de massa (LC-MS/MS) de uma forma não segmentados. A última estratégia muitas vezes é negativamente afetada por um grande número de falsos positivos descobertas, principalmente derivada da alta sensibilidade dos espectrômetros de massa modernas que confiantemente detectar vestígios de proteínas não específica precipitantes. A Recent abordagem para ultrapassar este problema é baseada na ideia de que quantidades reduzidas de parceiros específicos de interacção irá co-precipitado com uma dada proteína alvo, cuja concentração celular é reduzido por RNAi, enquanto as quantidades de proteínas não específica, não deve ser afectada precipitantes. Esta abordagem, chamada QUICK por imunoprecipitação quantitativos em conjunto com Knockdown 4, emprega Labeling isótopo estável de Aminoácidos em cultura celular (SILAC) 5 e MS para quantificar as quantidades de proteínas imunoprecipitadas a partir de estirpes do tipo selvagem e knock-down. Proteínas encontradas em uma proporção de 1:1 podem ser considerados como contaminantes, aqueles enriquecidos em precipitados a partir do tipo selvagem, como parceiros específicos de interacção da proteína alvo. Embora inovador, QUICK possui algumas limitações: em primeiro lugar, é SILAC custo intensivo e limitado para os organismos que, idealmente, são auxotróficas para arginina e / ou lisina. Além disso, quando a arginina pesado é alimentada, a arginina-to-proline resultados de interconversão em additmassa ional desloca para cada prolina num péptido e dilui ligeiramente pesado com arginina luz, o que faz com que a quantificação mais tediosa e menos precisa 5,6. Em segundo lugar, QUICK requer que os anticorpos são titulados de tal forma que eles não se tornam saturado com a proteína alvo em extractos de knock-down mutantes. Aqui, apresentamos um protocolo modificado rápido que supera as limitações acima referidas do QUICK substituindo SILAC para a rotulagem 15 N metabólica e pela substituição de RNAi mediada por knock-down para afinidade modulação de interações proteína-proteína. Nós demonstrar a aplicabilidade do presente protocolo utilizando as unicelulares Chlamydomonas reinhardtii alga verde como organismo-modelo e o acompanhante HSP70B cloroplasto como proteína alvo 7 (Figura 1). HSP70s são conhecidos por interagir com determinados colegas de acompanhantes e substratos apenas no estado ADP 8. Nós explorar essa propriedade como um meio de verificar a específicainteração de HSP70B com seu fator de troca de nucleotídeos CGE1 9.

Watch this Scientific Journal Video about A Protocol for the Identification of Protein-protein Interactions Based on 15N Metabolic Labeling, Immunoprecipitation, Quantitative Mass Spectrometry and Aff

A Protocol for the Identification of Protein-protein Interactions Based on 15N Metabolic Labeling, Immunoprecipitation, Quantitative Mass Spectrometry and Affinity Modulation

Nós apresentamos uma variação da abordagem QUICK (Imunoprecipitação quantitativos em conjunto com Knockdown) que foi introduzida anteriormente para distinguir entre verdadeiros e falsos interacções proteína-proteína. A nossa abordagem é baseada<sup&gt; 15N</sup&gt; Marcação metabólica, a modulação da afinidade das interacções proteína-proteína com a presença / ausência de ATP, imunoprecipitação, e por espectrometria de massa quantitativo.

Um protocolo para a identificação de interações proteína-proteína Baseado<sup&gt; 15</sup&gt; Etiquetagem N Metabólica, imunoprecipitação, Quantitativa Espectrometria de Massa e Affinity Modulação

Protein-protein interactions are fundamental for many biological processes in the cell. Therefore, their characterization plays an important role in ...

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JoVE Journal

Biology

A Protocol for the Identification of Protein-protein Interactions Based on 15N Metabolic Labeling, Immunoprecipitation, Quantitative Mass Spectrometry and Affinity Modulation

20.4K visualizações.  Max Planck Institute of Molecular Plant Physiology. Nós apresentamos uma variação da abordagem QUICK (Imunoprecipitação quantitativos em conjunto com Knockdown) que foi introduzida anteriormente para distinguir entre verdadeiros e falsos interacções proteína-proteína. A nossa abordagem é baseada 15N Marcação metabólica, a modulação da afinidade das interacções proteína-proteína com a presença / ausência de ATP, imunoprecipitação, e por espectrometria de massa quantitativo.

Vídeo: A Protocol for the Identification of Protein-protein Interactions Based on 15N Metabolic Labeling, Immunoprecipitation, Quantitative Mass Spectrometry and Affinity Modulation

MALDI Sample Preparation: the Ultra Thin Layer Method

This video demonstrates the preparation of an ultra-thin matrix/analyte layer for analyzing peptides and proteins by Matrix-Assisted Laser Desorption Ionization Mass Spectrometry (MALDI-MS) 1,2. The ultra-thin layer method involves the production of a substrate layer of matrix crystals (alpha-cyano-4-hydroxycinnamic acid) on the sample plate, which serves as a seeding ground for subsequent crystallization of a matrix/analyte mixture. Advantages of the ultra-thin layer method over other sample deposition approaches (e.g. dried droplet) are that it provides (i) greater tolerance to impurities such as salts and detergents, (ii) better resolution, and (iii) higher spatial uniformity. This method is especially useful for the accurate mass determination of proteins. The protocol was initially developed and optimized for the analysis of membrane proteins and used to successfully analyze ion channels, metabolite transporters, and receptors, containing between 2 and 12 transmembrane domains 2. Since the original publication, it has also shown to be equally useful for the analysis of soluble proteins. Indeed, we have used it for a large number of proteins having a wide range of properties, including those with molecular masses as high as 380 kDa 3. It is currently our method of choice for the molecular mass analysis of all proteins. The described procedure consistently produces high-quality spectra, and it is sensitive, robust, and easy to implement.

This video demonstrates the preparation of an ultra-thin matrix/analyte layer for analyzing peptides and proteins by Matrix-Assisted Laser Desorption Ionization Mass Spectrometry (MALDI-MS).

MALDI preparação da amostra: o método de Camada Ultra Thin

This video demonstrates the preparation of an ultra-thin matrix/analyte layer for analyzing peptides and proteins by Matrix-Assisted Laser Desorption ...

Biologia

A Quantitative Assessment of The Yeast Lipidome using Electrospray Ionization Mass Spectrometry

Lipids are one of the major classes of biomolecules and play important roles membrane dynamics, energy storage, and signalling1-4. The budding yeast Saccharomyces cerevisiae, a genetically and biochemically manipulable unicellular eukaryote with annotated genome and very simple lipidome, is a valuable model for studying biological functions of various lipid species in multicellular eukaryotes2,3,5. S. cerevisiae has 10 major classes of lipids with chain lengths mainly of 16 or 18 carbon atoms and either zero or one degree of unsaturation6,7. Existing methods for lipid identification and quantification - such as high performance liquid chromatography, thin-layer chromatography, fluorescence microscopy, and gas chromatography followed by MS - are well established but have low sensitivity, insufficiently separate various molecular forms of lipids, require lipid derivitization prior to analysis, or can be quite time consuming. Here we present a detailed description of our experimental approach to solve these inherent limitations by using survey-scan ESI/MS for the identification and quantification of the entire complement of lipids in yeast cells. The described method does not require chromatographic separation of complex lipid mixtures recovered from yeast cells, thereby greatly accelerating the process of data acquisition. This method enables lipid identification and quantification at the concentrations as low as g/ml and has been successfully applied to assessing lipidomes of whole yeast cells and their purified organelles. Lipids extraction from whole yeast cells for using this method of lipid analysis takes two to three hours. It takes only five to ten minutes to run each sample of extracted and dried lipids on a Q-TOF mass spectrometer equipped with a nano-electrospray source.

We describe a new quantitative lipidomics method for identifying numerous lipid species in yeast using survey-scan electrospray ionization mass spectrometry (ESI/MS). This method exceeds currently available methods for lipid identification and quantification in the ability to resolve various molecular forms of lipids, sensitivity, and speed.

A avaliação quantitativa do Lipidome fermento usando Electrospray Espectrometria de Massa de Ionização

Lipids are one of the major classes of biomolecules and play important roles membrane dynamics, energy storage, and signalling1-4. The budding yeast ...

Identification of Protein Complexes in Escherichia coli using Sequential Peptide Affinity Purification in Combination with Tandem Mass Spectrometry

Since most cellular processes are mediated by macromolecular assemblies, the systematic identification of protein-protein interactions (PPI) and the identification of the subunit composition of multi-protein complexes can provide insight into gene function and enhance understanding of biological systems1, 2. Physical interactions can be mapped with high confidence vialarge-scale isolation and characterization of endogenous protein complexes under near-physiological conditions based on affinity purification of chromosomally-tagged proteins in combination with mass spectrometry (APMS). This approach has been successfully applied in evolutionarily diverse organisms, including yeast, flies, worms, mammalian cells, and bacteria1-6. In particular, we have generated a carboxy-terminal Sequential Peptide Affinity (SPA) dual tagging system for affinity-purifying native protein complexes from cultured gram-negative Escherichia coli, using genetically-tractable host laboratory strains that are well-suited for genome-wide investigations of the fundamental biology and conserved processes of prokaryotes1, 2, 7. Our SPA-tagging system is analogous to the tandem affinity purification method developed originally for yeast8, 9, and consists of a calmodulin binding peptide (CBP) followed by the cleavage site for the highly specific tobacco etch virus (TEV) protease and three copies of the FLAG epitope (3X FLAG), allowing for two consecutive rounds of affinity enrichment. After cassette amplification, sequence-specific linear PCR products encoding the SPA-tag and a selectable marker are integrated and expressed in frame as carboxy-terminal fusions in a DY330 background that is induced to transiently express a highly efficient heterologous bacteriophage lambda recombination system10. Subsequent dual-step purification using calmodulin and anti-FLAG affinity beads enables the highly selective and efficient recovery of even low abundance protein complexes from large-scale cultures. Tandem mass spectrometry is then used to identify the stably co-purifying proteins with high sensitivity (low nanogram detection limits).
Here, we describe detailed step-by-step procedures we commonly use for systematic protein tagging, purification and mass spectrometry-based analysis of soluble protein complexes from E. coli, which can be scaled up and potentially tailored to other bacterial species, including certain opportunistic pathogens that are amenable to recombineering. The resulting physical interactions can often reveal interesting unexpected components and connections suggesting novel mechanistic links. Integration of the PPI data with alternate molecular association data such as genetic (gene-gene) interactions and genomic-context (GC) predictions can facilitate elucidation of the global molecular organization of multi-protein complexes within biological pathways. The networks generated for E. coli can be used to gain insight into the functional architecture of orthologous gene products in other microbes for which functional annotations are currently lacking.

Identification of Protein Complexes in Escherichia coli using Sequential Peptide Affinity Purification in Combination with Tandem Mass Spectrometry

Affinity purification of tagged proteins in combination with mass spectrometry (APMS) is a powerful method for the systematic mapping of protein interaction networks and for investigating the mechanistic basis of biological processes. Here, we describe an optimized sequential peptide affinity (SPA) APMS procedure developed for the bacterium Escherichia coli that can be used to isolate and characterize stable multi-protein complexes to near homogeneity even starting from low copy numbers per cell.

Identificação de complexos de proteínas em<em&gt; Escherichia coli</em&gt; Utilizando a purificação por afinidade sequencial Peptide em combinação com espectrometria de massa tandem

Since most cellular processes are mediated by macromolecular assemblies, the systematic identification of protein-protein interactions (PPI) and the ...

A New Approach for the Comparative Analysis of Multiprotein Complexes Based on 15N Metabolic Labeling and Quantitative Mass Spectrometry

The introduced protocol provides a tool for the analysis of multiprotein complexes in the thylakoid membrane, by revealing insights into complex composition under different conditions. In this protocol the approach is demonstrated by comparing the composition of the protein complex responsible for cyclic electron flow (CEF) in Chlamydomonas reinhardtii, isolated from genetically different strains. The procedure comprises the isolation of thylakoid membranes, followed by their separation into multiprotein complexes by sucrose density gradient centrifugation, SDS-PAGE, immunodetection and comparative, quantitative mass spectrometry (MS) based on differential metabolic labeling (14N/15N) of the analyzed strains. Detergent solubilized thylakoid membranes are loaded on sucrose density gradients at equal chlorophyll concentration. After ultracentrifugation, the gradients are separated into fractions, which are analyzed by mass-spectrometry based on equal volume. This approach allows the investigation of the composition within the gradient fractions and moreover to analyze the migration behavior of different proteins, especially focusing on ANR1, CAS, and PGRL1. Furthermore, this method is demonstrated by confirming the results with immunoblotting and additionally by supporting the findings from previous studies (the identification and PSI-dependent migration of proteins that were previously described to be part of the CEF-supercomplex such as PGRL1, FNR, and cyt f). Notably, this approach is applicable to address a broad range of questions for which this protocol can be adopted and e.g. used for comparative analyses of multiprotein complex composition isolated from distinct environmental conditions.

A New Approach for the Comparative Analysis of Multiprotein Complexes Based on 15N Metabolic Labeling and Quantitative Mass Spectrometry

The described comparative, quantitative proteomic approach aims at obtaining insights into the composition of multiprotein complexes&#160;under different conditions and is demonstrated by comparing genetically different strains. For quantitative analysis equal volumes of different fractions from a sucrose density gradient are mixed and analyzed by mass spectrometry.

Uma Nova Abordagem para a Análise Comparativa de Complexos Multiproteicos Baseado em<sup&gt; 15</sup&gt; N Metabólica Labeling e quantitativa Espectrometria de Massa

The introduced protocol provides a tool for the analysis of multiprotein complexes in the thylakoid membrane, by revealing insights into complex ...

Investigating Protein-protein Interactions in Live Cells Using Bioluminescence Resonance Energy Transfer

Assays based on Bioluminescence Resonance Energy Transfer (BRET) provide a sensitive and reliable means to monitor protein-protein interactions in live cells. BRET is the non-radiative transfer of energy from a 'donor' luciferase enzyme to an 'acceptor' fluorescent protein. In the most common configuration of this assay, the donor is Renilla reniformis luciferase and the acceptor is Yellow Fluorescent Protein (YFP). Because the efficiency of energy transfer is strongly distance-dependent, observation of the BRET phenomenon requires that the donor and acceptor be in close proximity. To test for an interaction between two proteins of interest in cultured mammalian cells, one protein is expressed as a fusion with luciferase and the second as a fusion with YFP. An interaction between the two proteins of interest may bring the donor and acceptor sufficiently close for energy transfer to occur. Compared to other techniques for investigating protein-protein interactions, the BRET assay is sensitive, requires little hands-on time and few reagents, and is able to detect interactions which are weak, transient, or dependent on the biochemical environment found within a live cell. It is therefore an ideal approach for confirming putative interactions suggested by yeast two-hybrid or mass spectrometry proteomics studies, and in addition it is well-suited for mapping interacting regions, assessing the effect of post-translational modifications on protein-protein interactions, and evaluating the impact of mutations identified in patient DNA.

Interactions between proteins are fundamental to all cellular processes. Using Bioluminescence Resonance Energy Transfer, the interaction between a pair of proteins can be monitored in live cells and in real time. Furthermore, the effects of potentially pathogenic mutations can be assessed.

Investigando interações proteína-proteína em células vivas usando a transferência de Bioluminescência Resonance Energy

Assays based on Bioluminescence Resonance Energy Transfer (BRET) provide a sensitive and reliable means to monitor protein-protein interactions in live ...

Chromatin Immunoprecipitation Assay for the Identification of Arabidopsis Protein-DNA Interactions In Vivo

Intricate gene regulatory networks orchestrate biological processes and developmental transitions in plants. Selective transcriptional activation and silencing of genes mediate the response of plants to environmental signals and developmental cues. Therefore, insights into the mechanisms that control plant gene expression are essential to gain a deep understanding of how biological processes are regulated in plants. The chromatin immunoprecipitation (ChIP) technique described here is a procedure to identify the DNA-binding sites of proteins in genes or genomic regions of the model species Arabidopsis thaliana. The interactions with DNA of proteins of interest such as transcription factors, chromatin proteins or posttranslationally modified versions of histones can be efficiently analyzed with the ChIP protocol. This method is based on the fixation of protein-DNA interactions in vivo, random fragmentation of chromatin, immunoprecipitation of protein-DNA complexes with specific antibodies, and quantification of the DNA associated with the protein of interest by PCR techniques. The use of this methodology in Arabidopsis has contributed significantly to unveil transcriptional regulatory mechanisms that control a variety of plant biological processes. This approach allowed the identification of the binding sites of the Arabidopsis chromatin protein EBS to regulatory regions of the master gene of flowering FT. The impact of this protein in the accumulation of particular histone marks in the genomic region of FT was also revealed through ChIP analysis.

Chromatin Immunoprecipitation Assay for the Identification of Arabidopsis Protein-DNA Interactions In Vivo

Chromatin immunoprecipitation is a powerful technique for the identification of DNA binding sites of Arabidopsis proteins in vivo. This procedure includes chromatin cross-linking and fragmentation, immunoprecipitation with selective antibodies against the protein of interest, and qPCR analysis of bound DNA. We describe a simple ChIP assay optimized for Arabidopsis plants.

Ensaio para imunoprecipitação da cromatina a identificação de Arabidopsis interações proteína-ADN<em&gt; In Vivo</em

Intricate gene regulatory networks orchestrate biological processes and developmental transitions in plants. Selective transcriptional activation and ...

Identification of MyoD Interactome Using Tandem Affinity Purification Coupled to Mass Spectrometry

Skeletal muscle terminal differentiation starts with the commitment of pluripotent mesodermal precursor cells to myoblasts. These cells have still the ability to proliferate or they can differentiate and fuse into multinucleated myotubes, which maturate further to form myofibers. Skeletal muscle terminal differentiation is orchestrated by the coordinated action of various transcription factors, in particular the members of the Muscle Regulatory Factors or MRFs (MyoD, Myogenin, Myf5, and MRF4), also called the myogenic bHLH transcription factors family. These factors cooperate with chromatin-remodeling complexes within elaborate transcriptional regulatory network to achieve skeletal myogenesis. In this, MyoD is considered the master myogenic transcription factor in triggering muscle terminal differentiation. This notion is strengthened by the ability of MyoD to convert non-muscle cells into skeletal muscle cells. Here we describe an approach used to identify MyoD protein partners in an exhaustive manner in order to elucidate the different factors involved in skeletal muscle terminal differentiation. The long-term aim is to understand the epigenetic mechanisms involved in the regulation of skeletal muscle genes, i.e., MyoD targets. MyoD partners are identified by using Tandem Affinity Purification (TAP-Tag) from a heterologous system coupled to mass spectrometry (MS) characterization, followed by validation of the role of relevant partners during skeletal muscle terminal differentiation. Aberrant forms of myogenic factors, or their aberrant regulation, are associated with a number of muscle disorders: congenital myasthenia, myotonic dystrophy, rhabdomyosarcoma and defects in muscle regeneration. As such, myogenic factors provide a pool of potential therapeutic targets in muscle disorders, both with regard to mechanisms that cause disease itself and regenerative mechanisms that can improve disease treatment. Thus, the detailed understanding of the intermolecular interactions and the genetic programs controlled by the myogenic factors is essential for the rational design of efficient therapies.

MyoD is a myogenic transcription factor with a strong capacity to induce myogenic transdifferentiation of many fully differentiated non-muscle cell lines. The epigenetic mechanisms involved in this transdifferentiation are largely unknown. Here we describe a double-affinity purification method followed by mass spectrometry to exhaustively characterize MyoD partners.

Identificação de MyoD interactome Usando purificação de afinidade em tandem Acoplado a Espectrometria de Massa

Skeletal muscle terminal differentiation starts with the commitment of pluripotent mesodermal precursor cells to myoblasts. These cells have still the ...

Study of Protein-protein Interactions in Autophagy Research

Protein-protein interactions are important for understanding cellular signaling cascades and identifying novel pathway components and protein dynamics. The majority of cellular activities require physical interactions between proteins. To analyze and map these interactions, various experimental techniques as well as bioinformatics tools were developed. Autophagy is a cellular recycling mechanism that allows the cells to cope with different stressors, including nutrient deprivation, chemicals, and hypoxia. In order to better understand autophagy-related signaling events and to discover novel factors that regulate protein complexes in autophagy, we performed protein-protein interaction screens. Validation of these screening results requires the use of immunofluorescence and immunoprecipitation techniques. In this system, specific autophagy-related protein-protein interactions that we discovered were tested in Neuro2A (N2A) and HEK293T cell lines. Details of the technical procedures used are explained in this visualized experiment paper.

Presented here are two antibody-based protein-protein interaction research techniques: immunofluorescence and immunoprecipitation. These techniques are suitable for studying physical interactions between proteins for the discovery of novel components of cellular signaling pathways and for understanding protein dynamics.

Estudo das interações proteína-proteína em pesquisa de autofagia

Protein-protein interactions are important for understanding cellular signaling cascades and identifying novel pathway components and protein dynamics. ...

Quantification of Site-specific Protein Lysine Acetylation and Succinylation Stoichiometry Using Data-independent Acquisition Mass Spectrometry

Post-translational modification (PTM) of protein lysine residues by N&#400;-acylation induces structural changes that can dynamically regulate protein functions, for example, by changing enzymatic activity or by mediating interactions. Precise quantification of site-specific protein acylation occupancy, or stoichiometry, is essential for understanding the functional consequences of both global low-level stoichiometry and individual high-level acylation stoichiometry of specific lysine residues. Other groups have reported measurement of lysine acetylation stoichiometry by comparing the ratio of peptide precursor isotopes from endogenous, natural abundance acylation and exogenous, heavy isotope-labeled acylation introduced after quantitative chemical acetylation of proteins using stable isotope-labeled acetic anhydride. This protocol describes an optimized approach featuring several improvements, including: (1) increased chemical acylation efficiency, (2) the ability to measure protein succinylation in addition to acetylation, and (3) improved quantitative accuracy due to reduced interferences using fragment ion quantification from data-independent acquisitions (DIA) instead of precursor ion signal from data-dependent acquisition (DDA). The use of extracted peak areas from fragment ions for quantification also uniquely enables differentiation of site-level acylation stoichiometry from proteolytic peptides containing more than one lysine residue, which is not possible using precursor ion signals for quantification. Data visualization in Skyline, an open source quantitative proteomics environment, allows for convenient data inspection and review. Together, this workflow offers unbiased, precise, and accurate quantification of site-specific lysine acetylation and succinylation occupancy of an entire proteome, which may reveal and prioritize biologically relevant acylation sites.

Here, we present unbiased quantification of site-specific protein acetylation and/or succinylation occupancy (stoichiometry) of an entire proteome through a ratiometric analysis of endogenous modifications to modifications introduced after quantitative chemical acylation using stable isotope-labeled anhydrides. In combination with sensitive data-independent acquisition mass spectrometry, accurate site occupancy measurements are obtained.

Quantificação de Estoicometria de Acetilação e Succinilação de Lisinas Proteicas em Sítios Específicos Usando Espectrometria de Massa de Aquisição de Dados Independente

Post-translational modification (PTM) of protein lysine residues by N&#400;-acylation induces structural changes that can dynamically regulate protein ...

SA-&#946;-Galactosidase-Based Screening Assay for the Identification of Senotherapeutic Drugs

Cell senescence is one of the hallmarks of aging known to negatively influence a healthy lifespan. Drugs able to kill senescent cells specifically in cell culture, termed senolytics, can reduce the senescent cell burden in vivo and extend healthspan. Multiple classes of senolytics have been identified to date including HSP90 inhibitors, Bcl-2 family inhibitors, piperlongumine, a FOXO4 inhibitory peptide and the combination of Dasatinib/Quercetin. Detection of SA-&#946;-Gal at an increased lysosomal pH is one of the best characterized markers for the detection of senescent cells. Live cell measurements of senescence-associated &#946;-galactosidase (SA-&#946;-Gal) activity using the fluorescent substrate C12FDG in combination with the determination of the total cell number using a DNA intercalating Hoechst dye opens the possibility to screen for senotherapeutic drugs that either reduce overall SA-&#946;-Gal activity by killing of senescent cells (senolytics) or by suppressing SA-&#946;-Gal and other phenotypes of senescent cells (senomorphics). Use of a high content fluorescent image acquisition and analysis platform allows for the rapid, high throughput screening of drug libraries for effects on SA-&#946;-Gal, cell morphology and cell number.

SA-&amp;#946;-Galactosidase-Based Screening Assay for the Identification of Senotherapeutic Drugs

Cellular senescence is the key factor in the development of chronic age-related pathologies. Identification of therapeutics that target senescent cells show promise for extending healthy aging. Here, we present a novel assay to screen for the identification of senotherapeutics based on measurement of senescence associated &#946;-Galactosidase activity in single cells.

Ensaio de triagem à base de SA-β-galactosidase para a identificação de medicamentos Senoterapêuticos

Cell senescence is one of the hallmarks of aging known to negatively influence a healthy lifespan. Drugs able to kill senescent cells specifically in cell ...