Les auteurs aimeraient remercier la Dre Jennifer Geddes-McAlister et le Dr Anthony Clarke pour leur contribution au perfectionnement de ce protocole. Ces travaux ont été appuyés par des subventions de fonctionnement des IRSC accordées au C.M.K (PJT 156111) et une BESC Alexander Graham Bell du CRSNG décernée à l’EMA. Des figures ont été créées le BioRender.com.

<ol>
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Microbiology. 10 (2), 123-136 (2011).</li><li>Yadav, A. K., Espaillat, A., Cava, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+strategies+to+preserve+cell+wall+integrity+against+environmental+threats.">Bacterial strategies to preserve cell wall integrity against environmental threats.</a> Frontiers in Microbiology. 9, 2064 (2018).</li><li>Bera, A., Herbert, S., Jakob, A., Vollmer, W., G&#246;tz, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Why+are+pathogenic+staphylococci+so+lysozyme+resistant?+The+peptidoglycan+O-acetyltransferase+OatA+is+the+major+determinant+for+lysozyme+resistance+of+Staphylococcus+aureus.">Why are pathogenic staphylococci so lysozyme resistant? 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Les auteurs ne déclarent aucun conflit d’intérêts.

Ce protocole décrit une méthode pour purifier le peptidoglycane à partir de cultures bactériennes, un procédé de détection LC-MS et une analyse de composition à l’aide de techniques bioinformatiques. Ici, nous nous concentrons sur les bactéries à Gram négatif et quelques légères modifications seront nécessaires pour permettre l’analyse des bactéries à Gram positif.
La préparation des muropeptides est restée pratiquement la même depuis sa première production dans les ann...

Le peptidoglycane (PG) est une caractéristique déterminante des bactéries qui sert à maintenir la morphologie cellulaire, tout en fournissant un soutien structurel aux protéines et autres composants cellulaires 1,2. L’épine dorsale du PG est composée d’acide muramique N-acétyl lié au β-1,4-1,4 (MurNAc) et de N-acétyl glucosamine (GlcNAc)1,2. Chaque MurNAc possède un peptide court lié au résidu ᴅ-lactyle qui peut être réticulé avec des peptides adjacents liés au disaccharide (Figure 1A,B). Cette réticulation produit une structure en forme de maille qui englobe toute la cellule et est souvent appelée sacculus (Figure 1C). Au cours de la synthèse du PG, des précurseurs sont générés dans le cytoplasme et transportés à travers la membrane cytoplasmique par des flippases. Les précurseurs sont ensuite incorporés dans le PG mature par les enzymes transglycosylase et transpeptidase, qui produisent respectivementles liaisons glycosidique et peptidique3. Cependant, une fois assemblées, il existe de nombreuses enzymes produites par les bactéries qui modifient et / ou dégradent le PG pour effectuer un certain nombre de processus cellulaires, y compris la croissance et la division. En outre, il a été démontré que diverses modifications du PG confèrent des adaptations spécifiques à la souche, aux conditions de croissance et au stress environnemental, qui ont été impliquées dans la signalisation cellulaire, la résistance aux antimicrobiens et l’évasion immunitaire de l’hôte4. À titre d’exemple, une modification courante est l’ajout d’un groupe acétyle C6 sur le MurNAc qui confère une résistance en limitant l’accès aux liaisons glycane β-1,4 aux enzymes lysozymes produites par l’hôte qui dégradent PG 4,5,6. Chez les entérocoques, la substitution du ᴅ-Ala terminal de la chaîne latérale peptidique par ᴅ-Lac confère une plus grande résistance à l’antimicrobien, la vancomycine 7,8.
La procédure générale d’isolement et de purification des PG est restée relativement inchangée depuis qu’elle a été décrite dans les années 19609. Les membranes bactériennes sont dissoutes par traitement thermique avec SDS, suivi de l’élimination enzymatique des protéines liées, des glycolipides et de l’ADN restant. Le sacculus intact purifié peut ensuite être digéré en composants individuels par hydrolyse de la liaison β-1,4 entre GlcNAc et MurNAc. Cette digestion produit des disaccharides GlcNAc-MurNAc avec toutes les modifications structurelles et / ou réticulations intactes et sont appelés muropeptides (Figure 1B).
L’analyse de la composition du PG a d’abord été réalisée par séparation chromatographique liquide à haute pression (CLHP) pour purifier chaque muropeptide, suivie d’une identification manuelle des muropeptides10,11. Cela a depuis été remplacé par la spectrométrie de masse en tandem par chromatographie liquide (LC-MS), qui augmente la sensibilité de détection et diminue la charge de travail manuelle de purification de chaque muropeptide individuel. Cependant, la nature longue et complexe de l’identification manuelle des muropeptides est restée un facteur limitant, réduisant le nombre d’études menées. Ces dernières années, avec l’émergence des technologies « omiques », l’extraction automatisée de caractéristiques LC-MS est devenue un outil puissant, permettant la détection et l’identification rapides de composés individuels dans des échantillons complexes à partir de très grands ensembles de données. Une fois les caractéristiques identifiées, le logiciel bioinformatique compare statistiquement la variation entre les échantillons à l’aide d’une analyse différentielle isolant même les différences minimes entre les ensembles de données complexes et les affichant graphiquement à l’utilisateur. L’application de logiciels d’extraction de caractéristiques pour l’analyse de la composition PG vient tout juste de commencer à être explorée 12,13,14 et couplée à l’analyse bioinformatique 12. Contrairement à l’analyse protéomique qui bénéficie des bases de données de protéines facilement disponibles qui prédisent la fragmentation peptidique permettant une identification entièrement automatisée, il n’existe actuellement aucune bibliothèque de fragmentation pour la peptidoglycomie. Cependant, l’extraction de caractéristiques peut être couplée à des bases de données structurelles connues et prévues pour prédire l’identification des muropeptides12. Nous présentons ici un protocole détaillé pour l’utilisation de l’extraction de caractéristiques à base de LC-MS combinée à une bibliothèque de muropeptides pour l’identification automatisée et l’analyse différentielle bioinformatique de la composition PG (Figure 2).

<table>
	<tbody>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>C18 reverse phase column - AdvanceBio Peptide column (100 mm x 2.1 mm 2.7 &#181;m)</td>
			<td>Agilent</td>
			<td></td>
			<td>LC-MS data acquisition</td>
		</tr>
		<tr>
			<td>Heating mantle controller, Optichem</td>
			<td>Fisher</td>
			<td>50-401-788</td>
			<td>for 4% SDS boil</td>
		</tr>
		<tr>
			<td>Heating Mantle, 1000mL Hemispherical</td>
			<td>Fisher</td>
			<td>CG1000008</td>
			<td>for 4% SDS boil</td>
		</tr>
		<tr>
			<td>Incubator, 37&#176;C</td>
			<td></td>
			<td></td>
			<td>for sacculi purification and MS sample prep</td>
		</tr>
		<tr>
			<td>Leibig condenser, 300MM 24/40,</td>
			<td>Fisher</td>
			<td>CG121805</td>
			<td>for 4% SDS boil</td>
		</tr>
		<tr>
			<td>Lyophilizer</td>
			<td>Labconco</td>
			<td></td>
			<td>for lyophilization of sacculi</td>
		</tr>
		<tr>
			<td>Magentic stirrer</td>
			<td>Fisher</td>
			<td>90-691-18</td>
			<td>for 4% SDS boil</td>
		</tr>
		<tr>
			<td>mass spectrometer Q-Tof model UHD 6530</td>
			<td>Aglient</td>
			<td></td>
			<td>LC-MS data acquisition</td>
		</tr>
		<tr>
			<td>microcentrifuge filters, Nanosep MF 0.2 &#181;m</td>
			<td>Fisher</td>
			<td>50-197-9573</td>
			<td>cleanup of sample before MS injection</td>
		</tr>
		<tr>
			<td>Retort stand</td>
			<td>Fisher</td>
			<td>12-000-102</td>
			<td>for 4% SDS boil</td>
		</tr>
		<tr>
			<td>Retort clamp</td>
			<td>Fisher</td>
			<td>S02629</td>
			<td>for 4% SDS boil</td>
		</tr>
		<tr>
			<td>round bottom flask - 1 liter pyrex</td>
			<td>Fisher</td>
			<td>07-250-084</td>
			<td>for 4% SDS boil</td>
		</tr>
		<tr>
			<td>Sonicator model 120</td>
			<td>Fisher</td>
			<td>FB120</td>
			<td>for sacculi purification</td>
		</tr>
		<tr>
			<td>Sonicator - micro tip</td>
			<td>Fisher</td>
			<td>FB4422</td>
			<td>for sacculi purification</td>
		</tr>
		<tr>
			<td>Ultracentrifuge</td>
			<td>Beckman</td>
			<td></td>
			<td>sacculi wash steps</td>
		</tr>
		<tr>
			<td>Ultracentrifuge bottles, Ti45</td>
			<td>Fisher</td>
			<td>NC9691797</td>
			<td>sacculi wash steps</td>
		</tr>
		<tr>
			<td>Water supply</td>
			<td>City</td>
			<td></td>
			<td>for water cooled condenser</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Chemdraw</td>
			<td>Cambridgesoft</td>
			<td></td>
			<td>molecular editor for muropeptide fragmentation prediction</td>
		</tr>
		<tr>
			<td>Excel</td>
			<td>Microsoft</td>
			<td></td>
			<td>viewing lists of annotated muropeptides, abundance, isotopic patterns, etc.</td>
		</tr>
		<tr>
			<td>MassHunter Acquisition</td>
			<td>Aglient</td>
			<td></td>
			<td>running QTOF instrument</td>
		</tr>
		<tr>
			<td>MassHunter Mass Profiler Professional</td>
			<td>Aglient</td>
			<td></td>
			<td>bioinformatic differential analysis</td>
		</tr>
		<tr>
			<td>MassHunter Personal Compound Database and Library Manager</td>
			<td>Aglient</td>
			<td></td>
			<td>muropeptide m/z MS database</td>
		</tr>
		<tr>
			<td>MassHunter Profinder</td>
			<td>Aglient</td>
			<td></td>
			<td>recursive feature extraction</td>
		</tr>
		<tr>
			<td>MassHunter Qualitative analysis</td>
			<td>Aglient</td>
			<td></td>
			<td>viewing MS and MS/MS chromatograms</td>
		</tr>
		<tr>
			<td>Prism</td>
			<td>Graphpad</td>
			<td></td>
			<td>Graphing software</td>
		</tr>
		<tr>
			<td>Perseus</td>
			<td>Max Plank Institute of Biochemistry</td>
			<td></td>
			<td>1D annotation</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Material</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Acetonitrile</td>
			<td>Fisher</td>
			<td>A998-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium acetate</td>
			<td>Fisher</td>
			<td>A637</td>
			<td></td>
		</tr>
		<tr>
			<td>Amylase</td>
			<td>Sigma-Aldrich</td>
			<td>A6380</td>
			<td></td>
		</tr>
		<tr>
			<td>Boric acid</td>
			<td>Fisher</td>
			<td>BP168-1</td>
			<td></td>
		</tr>
		<tr>
			<td>DNase</td>
			<td>Fisher</td>
			<td>EN0521</td>
			<td></td>
		</tr>
		<tr>
			<td>Formic acid</td>
			<td>Sigma-Aldrich</td>
			<td>27001-500ML-R</td>
			<td></td>
		</tr>
		<tr>
			<td>LC-MS tuning mix - HP0321</td>
			<td>Agilent</td>
			<td>G1969-85000</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium chloride</td>
			<td>Sigma-Aldrich</td>
			<td>M8266</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium sulfate</td>
			<td>Sigma-Aldrich</td>
			<td>M7506</td>
			<td></td>
		</tr>
		<tr>
			<td>Mutanolysin from Streptomyces globisporus ATCC 21553</td>
			<td>Sigma-Aldrich</td>
			<td>M9901</td>
			<td></td>
		</tr>
		<tr>
			<td>Nitrogen gas (&#62;99% purity)</td>
			<td>Praxair</td>
			<td>NI 5.0UH-T</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphoric acid</td>
			<td>Fisher</td>
			<td>A242</td>
			<td></td>
		</tr>
		<tr>
			<td>Pronase E from Streptomyces griseus</td>
			<td>Sigma-Aldrich</td>
			<td>P5147</td>
			<td></td>
		</tr>
		<tr>
			<td>RNase</td>
			<td>Fisher</td>
			<td>EN0531</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium azide</td>
			<td>Fisher</td>
			<td>S0489</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium borohydride</td>
			<td>Sigma-Aldrich</td>
			<td>452890</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium dodecyl sulfate (SDS)</td>
			<td>Fisher</td>
			<td>BP166</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>Fisher</td>
			<td>S318</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Phosphate (dibasic)</td>
			<td>Fisher</td>
			<td>S373</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Phosphate (monobasic)</td>
			<td>Fisher</td>
			<td>S369</td>
			<td></td>
		</tr>
		<tr>
			<td>Stains-all</td>
			<td>Sigma-Aldrich</td>
			<td>E9379</td>
			<td></td>
		</tr>
	</tbody>
</table>

semi-quantitative analysis of peptidoglycan by liquid chromatography mass spectrometry and bioinformatics

Le peptidoglycane est un composant important des parois cellulaires bactériennes et une cible cellulaire commune pour les antimicrobiens. Bien que certains aspects de la structure du peptidoglycane soient assez conservés dans toutes les bactéries, il existe également des variations considérables entre les Gram positifs/négatifs et entre les espèces. En outre, il existe de nombreuses variations, modifications ou adaptations connues du peptidoglycane qui peuvent se produire au sein d’une espèce bactérienne en réponse à une phase de croissance et / ou à des stimuli environnementaux. Ces variations produisent une structure très dynamique qui est connue pour participer à de nombreuses fonctions cellulaires, y compris la croissance / division, la résistance aux antibiotiques et l’évitement de la défense de l’hôte. Pour comprendre la variation au sein du peptidoglycane, la structure globale doit être décomposée en ses parties constitutives (appelées muropeptides) et évaluée pour la composition cellulaire globale. La peptidoglycomique utilise la spectrométrie de masse avancée combinée à une analyse de données bioinformatiques de haute puissance pour examiner la composition du peptidoglycane dans les moindres détails. Le protocole suivant décrit la purification du peptidoglycane à partir de cultures bactériennes, l’acquisition de données d’intensité de muropeptides par chromatographe liquide – spectromètre de masse et l’analyse différentielle de la composition du peptidoglycane à l’aide de la bioinformatique.

La sensibilité accrue de détection des machines MS associée à un logiciel de reconnaissance de pics très puissant a amélioré la capacité d’isoler, de surveiller et d’analyser les compositions de substances d’échantillons complexes dans les moindres détails. Grâce à ces avancées technologiques, des études récentes sur la composition du peptidoglycane ont commencé à utiliser des techniques automatisées d’extraction de caractéristiques LC-MS 12,13,14,24 par rapport à l’ancienne méthodologie ba...

Watch this Scientific Journal Video about Semi-Quantitative Analysis of Peptidoglycan by Liquid Chromatography Mass Spectrometry and Bioinformatics at JoVE.com

Semi-Quantitative Analysis of Peptidoglycan by Liquid Chromatography Mass Spectrometry and Bioinformatics

Ce protocole couvre une analyse détaillée de la composition du peptidoglycane à l’aide de la spectrométrie de masse par chromatographie liquide couplée à un logiciel avancé d’extraction de caractéristiques et d’analyse bioinformatique.

Analyse semi-quantitative du peptidoglycane par chromatographie liquide Spectrométrie de masse et bioinformatique

Peptidoglycan is an important component of bacterial cell walls and a common cellular target for antimicrobials. Although aspects of peptidoglycan ...

semi-quantitative-analysis-peptidoglycan-liquid-chromatography-mass

Research

JoVE Journal

Biochemistry

4.1K vues.  University of Guelph. Ce protocole couvre une analyse détaillée de la composition du peptidoglycane à l’aide de la spectrométrie de masse par chromatographie liquide couplée à un logiciel avancé d’extraction de caractéristiques et d’analyse bioinformatique.

Vidéo: Semi-Quantitative Analysis of Peptidoglycan by Liquid Chromatography Mass Spectrometry and Bioinformatics

Time-resolved ElectroSpray Ionization Hydrogen-deuterium Exchange Mass Spectrometry for Studying Protein Structure and Dynamics

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. Hydrogen-Deuterium Exchange (HDX) measured at rapid time scales is uniquely suited to detect structures and hydrogen bonding networks that are briefly populated, allowing for the characterization of transient conformers in native ensembles. Coupling of HDX to mass spectrometry offers several key advantages, including high sensitivity, low sample consumption and no restriction on protein size. This technique has advanced greatly in the last several decades, including the ability to monitor HDX labeling times on the millisecond time scale. In addition, by incorporating the HDX workflow onto a microfluidic platform housing an acidic protease microreactor, we are able to localize dynamic properties at the peptide level. In this study, Time-Resolved ElectroSpray Ionization Mass Spectrometry (TRESI-MS) coupled to HDX was used to provide a detailed picture of residual structure in the tau protein, as well as the conformational shifts induced upon hyperphosphorylation.

Conformational flexibility plays a critical role in protein function. Herein, we describe the use of time-resolved electrospray ionization mass spectrometry coupled to hydrogen-deuterium exchange for probing the rapid structural changes that drive function in ordered and disordered proteins.

Résolue en temps d&#39;échange hydrogène Ionisation ElectroSpray-deuterium spectrométrie de masse pour l&#39;étude de la structure des protéines et dynamique

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. ...

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Biochimie

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.

Here we present protocols for affinity purification of protein complexes and their separation by blue native PAGE, followed by protein correlation profiling using label free quantitative mass spectrometry. This method is useful to resolve interactomes into distinct protein complexes.

Résoudre les complexes protéiques purifiés par affinité de Blue native PAGE et le profilage de corrélation des protéines

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

A Tandem Liquid Chromatography&#8211;Mass Spectrometry-based Approach for Metabolite Analysis of Staphylococcus aureus

In an effort to thwart bacterial pathogens, hosts often limit the availability of nutrients at the site of infection. This limitation can alter the abundances of key metabolites to which regulatory factors respond, adjusting cellular metabolism. In recent years, a number of proteins and RNA have emerged as important regulators of virulence gene expression. For example, the CodY protein responds to levels of branched-chain amino acids and GTP and is widely conserved in low G+C Gram-positive bacteria. As a global regulator in Staphylococcus aureus, CodY controls the expression of dozens of virulence and metabolic genes. We hypothesize that S. aureus uses CodY, in part, to alter its metabolic state in an effort to adapt to nutrient-limiting conditions potentially encountered in the host environment. This manuscript describes a method for extracting and analyzing metabolites from S. aureus using liquid chromatography coupled with mass spectrometry, a protocol that was developed to test this hypothesis. The method also highlights best practices that will ensure rigor and reproducibility, such as maintaining biological steady state and constant aeration without the use of continuous chemostat cultures. Relative to the USA200 methicillin-susceptible S. aureus isolate UAMS-1 parental strain, the isogenic codY mutant exhibited significant increases in amino acids derived from aspartate (e.g., threonine and isoleucine) and decreases in their precursors (e.g., aspartate and O-acetylhomoserine). These findings correlate well with transcriptional data obtained with RNA-seq analysis: genes in these pathways were up-regulated between 10- and 800-fold in the codY null mutant. Coupling global analyses of the transcriptome and the metabolome can reveal how bacteria alter their metabolism when faced with environmental or nutritional stress, providing potential insight into the physiological changes associated with nutrient depletion experienced during infection. Such discoveries may pave the way for the development of novel anti-infectives and therapeutics.

A Tandem Liquid Chromatography&amp;#8211;Mass Spectrometry-based Approach for Metabolite Analysis of &lt;em&gt;Staphylococcus aureus&lt;/em&gt;

Here we describe a protocol for the extraction of metabolites from Staphylococcus aureus and their subsequent analysis via liquid chromatography and mass spectrometry.

Une approche fondée Spectrométrie liquide tandem chromatographie-masse pour l&#39;analyse des Métabolite<em&gt; Staphylococcus aureus</em

In an effort to thwart bacterial pathogens, hosts often limit the availability of nutrients at the site of infection. This limitation can alter the ...

Lipid Droplet Isolation for Quantitative Mass Spectrometry Analysis

Lipid droplets are vital to the replication of a variety of different pathogens, most prominently the Hepatitis C Virus (HCV), as the putative site of virion morphogenesis. Quantitative lipid droplet proteome analysis can be used to identify proteins that localize to or are displaced from lipid droplets under conditions such as virus infections. Here, we describe a protocol that has been successfully used to characterize the changes in the lipid droplet proteome following infection with HCV. We use Stable Isotope Labeling with Amino Acids in Cell Culture (SILAC) and thus label the complete proteome of one population of cells with &#34;heavy&#34; amino acids to quantitate the proteins by mass spectrometry. For lipid droplet isolation, the two cell populations (i.e.&#160;HCV-infected/&#34;light&#34; amino acids and uninfected control/&#34;heavy&#34; amino acids) are mixed 1:1 and lysed mechanically in hypotonic buffer. After removing the nuclei and cell debris by low speed centrifugation, lipid droplet-associated proteins are enriched by two subsequent ultracentrifugation steps followed by three washing steps in isotonic buffer. The purity of the lipid droplet fractions is analyzed by western blotting with antibodies recognizing different subcellular compartments. Lipid droplet-associated proteins are then separated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) followed by Coomassie staining. After tryptic digest, the peptides are quantified by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). Using this method, we identified proteins recruited to lipid droplets upon HCV infection that might represent pro- or antiviral host factors. Our method can be applied to a variety of different cells and culture conditions, such as infection with pathogens, environmental stress, or drug treatment.

Lipid droplets are important organelles for the replication of several pathogens, including the Hepatitis C Virus (HCV). We describe a method to isolate lipid droplets for quantitative mass spectrometry of associated proteins; it can be used under a variety of conditions, such as virus infection, environmental stress, or drug treatment.

Isolation Lipid Droplet pour l&#39;analyse quantitative de spectrométrie de masse

Lipid droplets are vital to the replication of a variety of different pathogens, most prominently the Hepatitis C Virus (HCV), as the putative site of ...

Deep Proteome Profiling by Isobaric Labeling, Extensive Liquid Chromatography, Mass Spectrometry, and Software-assisted Quantification

Many exceptional advances have been made in mass spectrometry (MS)-based proteomics, with particular technical progress in liquid chromatography (LC) coupled to tandem mass spectrometry (LC-MS/MS) and isobaric labeling multiplexing capacity. Here, we introduce a deep-proteomics profiling protocol that combines 10-plex tandem mass tag (TMT) labeling with an extensive LC/LC-MS/MS platform, and post-MS computational interference correction to accurately quantitate whole proteomes. This protocol includes the following main steps: protein extraction and digestion, TMT labeling, 2-dimensional (2D) LC, high-resolution mass spectrometry, and computational data processing. Quality control steps are included for troubleshooting and evaluating experimental variation. More than 10,000 proteins in mammalian samples can be confidently quantitated with this protocol. This protocol can also be applied to the quantitation of post translational modifications with minor changes. This multiplexed, robust method provides a powerful tool for proteomic analysis in a variety of complex samples, including cell culture, animal tissues, and human clinical specimens.

We present a protocol to accurately quantitate proteins with isobaric labelling, extensive fractionation, bioinformatics tools, and quality control steps in combination with liquid chromatography interfaced to a high-resolution mass spectrometer.

Profilage de Proteome profonde en étiquetage isobare, vaste chromatographie en phase liquide, spectrométrie de masse et Quantification assistée par logiciel

Many exceptional advances have been made in mass spectrometry (MS)-based proteomics, with particular technical progress in liquid chromatography (LC) ...

Detection of Protein Ubiquitination Sites by Peptide Enrichment and Mass Spectrometry

The posttranslational modification of proteins by the small protein ubiquitin is involved in many cellular events. After tryptic digestion of ubiquitinated proteins, peptides with a diglycine remnant conjugated to the epsilon amino group of lysine (&#39;K-&#949;-diglycine&#39; or simply &#39;diGly&#39;) can be used to track back the original modification site. Efficient immunopurification of diGly peptides combined with sensitive detection by mass spectrometry has resulted in a huge increase in the number of ubiquitination sites identified up to date. We have made several improvements to this workflow, including offline high pH reverse-phase fractionation of peptides prior to the enrichment procedure, and the inclusion of more advanced peptide fragmentation settings in the ion routing multipole. Also, more efficient cleanup of the sample using a filter-based plug in order to retain the antibody beads results in a greater specificity for diGly peptides. These improvements result in the routine detection of more than 23,000 diGly peptides from human cervical cancer cells (HeLa) cell lysates upon proteasome inhibition in the cell. We show the efficacy of this strategy for in-depth analysis of the ubiquitinome profiles of several different cell types and of in vivo samples, such as brain tissue. This study presents an original addition to the toolbox for protein ubiquitination analysis to uncover the deep cellular ubiquitinome.

We present a method for the purification, detection, and identification of diGly peptides that originate from ubiquitinated proteins from complex biological samples. The presented method is reproducible, robust, and outperforms published methods with respect to the level of depth of the ubiquitinome analysis.

Détection des sites d’ubiquitination des protéines par l’enrichissement du peptide et la spectrométrie de masse

The posttranslational modification of proteins by the small protein ubiquitin is involved in many cellular events. After tryptic digestion of ...

Nitropeptide Profiling and Identification Illustrated by Angiotensin II

Protein nitration is one of the most important post-translational modifications (PTM) on tyrosine residues and it can be induced by chemical actions of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in eukaryotic cells. Precise identification of nitration sites on proteins is crucial for understanding the physiological and pathological processes related to protein nitration, such as inflammation, aging, and cancer. Since the nitrated proteins are of low abundance in cells even under induced conditions, no universal and efficient methods have been developed for the profiling and identification of protein nitration sites. Here we describe a protocol for nitropeptide enrichment by using a chemical reduction reaction and biotin labeling, followed by high resolution mass spectrometry. In our method, nitropeptide derivatives can be identified with high accuracy. Our method exhibits two advantages compared to the previously reported methods. First, dimethyl labeling is used to block the primary amine on nitropeptides, which can be used to generate quantitative results. Second, a disulfide bond containing NHS-biotin reagent is used for the enrichment, which can be further reduced and alkylated to enhance the detection signal on a mass spectrometer. This protocol has been successfully applied to the model peptide Angiotensin II in the current paper.

Proteomic profiling of tyrosine-nitrated proteins has been a challenging technique due to the low abundance of the 3-nitrotyrosine modification. Here we describe a novel approach for nitropeptide enrichment and profiling by using Angiotensin II as the model. This method can be extended for other in vitro or in vivo systems.

Profilage et identification de Nitropeptide illustrépar Angiotensin II

Protein nitration is one of the most important post-translational modifications (PTM) on tyrosine residues and it can be induced by chemical actions of ...

Identification of Inositol Phosphate or Phosphoinositide Interacting Proteins by Affinity Chromatography Coupled to Western Blot or Mass Spectrometry

Inositol phosphates and phosphoinositides regulate several cellular processes in eukaryotes, including gene expression, vesicle trafficking, signal transduction, metabolism, and development. These metabolites perform this regulatory activity by binding to proteins, thereby changing protein conformation, catalytic activity, and/or interactions. The method described here uses affinity chromatography coupled to mass spectrometry or Western blotting to identify proteins that interact with inositol phosphates or phosphoinositides. Inositol phosphates or phosphoinositides are chemically tagged with biotin, which is then captured via streptavidin conjugated to agarose or magnetic beads. Proteins are isolated by their affinity of binding to the metabolite, then eluted and identified by mass spectrometry or Western blotting. The method has a simple workflow that is sensitive, non-radioactive, liposome-free, and customizable, supporting the analysis of protein and metabolite interaction with precision. This approach can be used in label-free or in amino acid-labelled quantitative mass spectrometry methods to identify protein-metabolite interactions in complex biological samples or using purified proteins. This protocol is optimized for the analysis of proteins from Trypanosoma brucei, but it can be adapted to related protozoan parasites, yeast or mammalian cells.

This protocol focuses on the identification of proteins that bind to inositol phosphates or phosphoinositides. It uses affinity chromatography with biotinylated inositol phosphates or phosphoinositides that are immobilized via streptavidin to agarose or magnetic beads. Inositol phosphate or phosphoinositide binding proteins are identified by Western blotting or mass spectrometry.

Identification du phosphate d'inositol ou du phosphoinositide Protéines interactatrices par chromatographie d'affinité couplée à la fente occidentale ou à la spectrométrie de masse

Inositol phosphates and phosphoinositides regulate several cellular processes in eukaryotes, including gene expression, vesicle trafficking, signal ...

Absolute Quantification of Cell-Free Protein Synthesis Metabolism by Reversed-Phase Liquid Chromatography-Mass Spectrometry

Cell-free protein synthesis (CFPS) is an emerging technology in systems and synthetic biology for the in vitro production of proteins. However, if CFPS is going to move beyond the laboratory and become a widespread and standard just in time manufacturing technology, we must understand the performance limits of these systems. Toward this question, we developed a robust protocol to quantify 40 compounds involved in glycolysis, the pentose phosphate pathway, the tricarboxylic acid cycle, energy metabolism and cofactor regeneration in CFPS reactions. The method uses internal standards tagged with 13C-aniline, while compounds in the sample are derivatized with 12C-aniline. The internal standards and sample were mixed and analyzed by reversed-phase liquid chromatography-mass spectrometry (LC/MS). The co-elution of compounds eliminated ion suppression, allowing the accurate quantification of metabolite concentrations over 2-3 orders of magnitude where the average correlation coefficient was 0.988. Five of the forty compounds were untagged with aniline, however, they were still detected in the CFPS sample and quantified with a standard curve method. The chromatographic run takes approximately 10 min to complete. Taken together, we developed a fast, robust method to separate and accurately quantify 40 compounds involved in CFPS in a single LC/MS run. The method is a comprehensive and accurate approach to characterize cell-free metabolism, so that ultimately, we can understand and improve the yield, productivity and energy efficiency of cell-free systems.

Here, we present a robust protocol to quantify 40 compounds involved in central carbon and energy metabolism in cell-free protein synthesis reactions. The cell-free synthesis mixture is derivatized with aniline for effective separation using reversed-phase liquid chromatography and then quantified by mass spectrometry using isotopically labelled internal standards.

Quantification absolue du métabolisme de synthèse des protéines sans cellules par spectrométrie de chromatographie liquide à phase inversée

Cell-free protein synthesis (CFPS) is an emerging technology in systems and synthetic biology for the in vitro production of proteins. However, if CFPS is ...

Quantitative Analysis of the Cellular Lipidome of Saccharomyces Cerevisiae Using Liquid Chromatography Coupled with Tandem Mass Spectrometry

Lipids are structurally diverse amphipathic molecules that are insoluble in water. Lipids are essential contributors to the organization and function of biological membranes, energy storage and production, cellular signaling, vesicular transport of proteins, organelle biogenesis, and regulated cell death. Because the budding yeast Saccharomyces cerevisiae is a unicellular eukaryote amenable to thorough molecular analyses, its use as a model organism helped uncover mechanisms linking lipid metabolism and intracellular transport to complex biological processes within eukaryotic cells. The availability of a versatile analytical method for the robust, sensitive, and accurate quantitative assessment of major classes of lipids within a yeast cell is crucial for getting deep insights into these mechanisms. Here we present a protocol to use liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) for the quantitative analysis of major cellular lipids of S. cerevisiae. The LC-MS/MS method described is versatile and robust. It enables the identification and quantification of numerous species (including different isobaric or isomeric forms) within each of the 10 lipid classes. This method is sensitive and allows identification and quantitation of some lipid species at concentrations as low as 0.2 pmol/&#181;L. The method has been successfully applied to assessing lipidomes of whole yeast cells and their purified organelles. The use of alternative mobile phase additives for electrospray ionization mass spectrometry in this method can increase the efficiency of ionization for some lipid species and can be therefore used to improve their identification and quantitation.

Quantitative Analysis of the Cellular Lipidome of Saccharomyces Cerevisiae Using Liquid Chromatography Coupled with Tandem Mass Spectrometry

We present a protocol using liquid chromatography coupled with tandem mass spectrometry to identify and quantify major cellular lipids in Saccharomyces cerevisiae. The described method for a quantitative assessment of major lipid classes within a yeast cell is versatile, robust, and sensitive.

Analyse quantitative du lipidome cellulaire de Saccharomyces Cerevisiae à l’aide de la chromatographie liquide couplée à la spectrométrie de masse tandem

Lipids are structurally diverse amphipathic molecules that are insoluble in water. Lipids are essential contributors to the organization and function of ...