Name: Multimer-PAGE: Ein Verfahren zum Erfassen und Auflösen von Proteinkomplexen in biologischen Proben (Video) | JoVE Journal
Uploaded: 2017-05-05T14:00:00.000+00:00
Duration: 7 min 40 s
Description: Erfahren Sie, wie Sie native Proteinkomplexe aus Gewebelysaten mit Multimer-PAGE stabilisieren und analysieren. Diese Methode ermöglicht die Erfassung labiler Proteinassoziationen unter nahezu nativen Bedingungen für die Proteomforschung.

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Supported by the NIH/NIDA DA034783. We thank Bryan A. Killinger for technical assistance with the multimer-PAGE.

1. Tissue Preparation
<ol>
	<li>Prepare 10 mL of 4x BN-PAGE sample buffer (200 mM Bis(2-hydroxyethyl)amino-tris(hydroxymethyl)methane (Bis-Tris), 200 mM NaCl, 40% w/v glycerol, 0.004% Ponceau S, pH 7.2). 
	NOTE: This stock solution may be made in advance and stored at 4 &#176;C.</li>
	<li>Dilute 250 &#181;L of 4x sample buffer in 750 &#181;L dH2O containing 1x commercial protease inhibitor cocktail. Vortex and chill on ice.</li>
	<li>Homogenize 20 mg of target tissue in the 1 mL 1x ice-cold BN-PAGE sample buffer with 30 strokes of a clean dounce homogenizer. 
	NOTE: For this demonstration experiment, the target tissue is whole rat brain tissue. After homogenization, samples may be treated with mild detergent such as 2% digitonin to solubilize and permit electrophoresis of membrane proteins.</li>
	<li>Transfer the homogenate to a 1.5 mL microcentrifuge tube, and centrifuge at 14,000 x g for 30 min to pellet insoluble cellular contents. After centrifugation, decant the supernatant into a clean tube on ice.</li>
	<li>Follow manufacturer instructions to measure supernatant protein concentration using bicinchoninic acid (BCA) or similar protein quantitation assay.</li>
	<li>If the homogenate sample(s) contain detergent, add a quantity of 5% Coomassie Blue G-250 in aqueous solution sufficient to bring the homogenate solution to 0.25% Coomassie.</li>
</ol>
2. BN-PAGE
<ol>
	<li>Dilute 25 mL 20x blue native (BN) electrophoresis buffer stock (1.0 M Bis-Tris, 1.0 M tricine, pH 6.8) into 475 mL dH2O containing 0.002% Coomassie Blue to make 500 mL of 1x running buffer.
	<ol>
		<li>If samples contain detergent, instead make 250 mL of 1x running buffer containing 0.02% Coomassie and another 250 mL containing none.</li>
	</ol>
	</li>
	<li>Chill buffer(s) to 4 &#176;C.</li>
	<li>Clean and assemble a polyacrylamide gel pouring cassette according to manufacturer instructions.</li>
	<li>Pour BN polyacrylamide gel (3% T stacking layer, 6% T resolving layer) according to a standard recipe7, and place the well comb.</li>
	<li>After the gels have polymerized, rinse the cassette with dH2O and assemble the electrophoresis apparatus according to manufacturer instructions.</li>
	<li>Remove the well comb and fill the wells with 1x BN-PAGE running buffer. Avoid filling the entire inner chamber with buffer until samples are loaded.
	<ol>
		<li>If samples contain detergent, fill the wells with the buffer containing 0.02% Coomassie Blue. 
		NOTE: Perform steps 2.7-2.9 at 4 &#176;C.</li>
	</ol>
	</li>
	<li>Using gel-loading tips, pipette a volume of homogenate containing 20 &#181;g of protein into the desired wells. Pipette an equivalent volume of 1x BN-PAGE sample buffer into any unused wells. 
	NOTE: Use the protein concentration determined from the BCA assay to calculate the appropriate volume of homogenate to add to the wells.</li>
	<li>After samples are loaded, fill the inner chamber with 1x BN-PAGE running buffer. Be sure the gel is entirely submerged in buffer. Next, fill the outer chamber with 1x running buffer to the level indicated by the manufacturer.
	<ol>
		<li>If samples contain detergent, fill the inner chamber with the 1x buffer containing 0.02% Coomassie Blue, and the outer chamber with dye-free 1x running buffer.</li>
	</ol>
	</li>
	<li>Connect the electrodes to the power supply, and electrophorese the proteins in the gel at 150 V until the dye band progresses ~2 cm into resolving layer. Stop and disconnect the power supply.</li>
</ol>
3. Cross-linking
NOTE: Perform Steps 3.1-3.6 at 4 &#176;C.
<ol>
	<li>Disassemble the electrophoresis apparatus, and separate the glass panes of the gel cassette. Remove and discard the stacking layer.</li>
	<li>Carefully cut the gel just below the bottom edge of the dye front. Take care to make this cut as smooth and straight as possible, and then discard the unused piece of gel. This will leave a ~2 cm wide, horizontal strip of polyacrylamide gel, which will contain all the protein in the homogenate sample.</li>
	<li>Trim away any unused portions along the edges of the gel strip.</li>
	<li>Carefully place the strip into 10 mL phosphate buffered saline (PBS) in a small container, and gently mix by nutation for 30 min to equilibrate.</li>
	<li>After equilibration, discard and replace the PBS with another 10 mL. Pipette 500 &#181;L of 25 mM DSP dissolved in dimethyl sulfoxide into the PBS, and continue mixing as above (step 3.4) for 30 min.</li>
	<li>Pour off the DSP solution. Add 10 mL of 0.375 M tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl), pH 8.8, containing 2% sodium dodecyl sulfate (SDS) to quench the unreacted DSP. Continue nutation for 15 min.</li>
</ol>
4. SDS-PAGE
<ol>
	<li>While gel strip is quenching, prepare SDS-PAGE gel solutions according to standard methods9. Do not add polymerization reagents.</li>
	<li>After quenching, return the &#914;&#925; gel strip to room temperature, and cast the strip into a new gel cassette.
	<ol>
		<li>To do this, carefully pick up the gel and place it onto a clean gel cassette spacer plate.</li>
		<li>Orient the strip so the bottom of the dye front is nearest to the top of new cassette (i.e., the side that travelled furthest during BN-PAGE should be closest to the top of the new cassette; the gel strip should be flipped from its prior orientation). See Figure 3.</li>
		<li>Place the strip such that its top edge lies even with where the top edge of the cover plate will be (i.e., it will be at the top of the new gel). Make sure the dye front is parallel to the horizontal edges of the glass plate.</li>
		<li>Push one side of the excised strip against one of the spacer walls, leaving room on the other side for gel to be poured and a protein standard or ladder to be loaded.</li>
		<li>If the bottom edge of the gel strip contains any jagged or uneven areas, carefully cut them away. If present, they will trap bubbles during gel pouring.</li>
		<li>Once the gel strip is positioned correctly, lay the cover plate over the spacer plate. Apply gentle pressure to push out any trapped air bubbles.</li>
		<li>Continue to assemble the gel-pouring apparatus according to manufacturer instructions.</li>
	</ol>
	</li>
	<li>Add polymerization reagents to the resolving gel buffer, and pour it into the prepared gel cassette, using a serological pipette. Fill the gel cassette to ~2 cm below the excised BN-PAGE gel strip, to leave room for the stacking layer.</li>
	<li>Add 100 &#181;L butanol over the top of the poured gel, and allow 30 min for polymerization of the resolving layer. Pour off the butanol.</li>
	<li>Add polymerization reagents to the stacking gel solution. Using a serological pipette, pour the stacking layer to fill all remaining empty space in the gel cassette.
	<ol>
		<li>Tilt the gel cassette as the stacking layer is poured so it fills the space below the gel strip, and air bubbles are not trapped.</li>
		<li>As the stacking gel buffer fills the empty space below the gel strip, gradually return the gel cassette to level footing.</li>
		<li>Continue to fill the empty space next to the excised gel strip with the stacking gel buffer, until it nearly overflows.</li>
	</ol>
	</li>
	<li>Allow the stacking layer to polymerize for 30 min. 
	NOTE: Make 10x SDS-PAGE running buffer (250 mM tris(hydroxymethyl)aminomethane (tris), 1.9 M glycine, 1% SDS) while the gel is polymerizing. This can also be made beforehand and stored at room temperature.</li>
	<li>Dilute 50 mL 10X SDS-PAGE running buffer stock into 450 mL dH2O to make 1x working buffer.</li>
	<li>After the stacking layer has polymerized, remove the gel cassette from the pouring apparatus, rinse with dH2O, and assemble the electrophoresis apparatus according to manufacturer instructions.</li>
	<li>Fill the inner chamber completely with 1x SDS-PAGE running buffer, then fill the outer chamber to the level indicated by the manufacturer.</li>
	<li>Load the space next to the excised gel strip with a molecular weight ladder or appropriate protein standard.</li>
	<li>Attach the electrodes to the power supply, and electrophorese the samples at 120 V. When the Coomassie dye runs off the gel, stop and disconnect the power supply.</li>
	<li>Analyze the gel using standard methods of electroblotting and protein detection by antibody binding10.</li>
</ol>

<ol><li>Alberts, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+cell+as+a+collection+of+protein+machines%3A+preparing+the+next+generation+of+molecular+biologists%5BTitle%5D)+AND+%22Cell%22%5BJournal%5D)">The cell as a collection of protein machines: preparing the next generation of molecular biologists.</a> Cell. 92 (3), 291-294 (1998).</li>
<li>Pawson, T., Nash, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Protein-protein+interactions+define+specificity+in+signal+transduction%5BTitle%5D)+AND+%22Genes+Dev%22%5BJournal%5D)">Protein-protein interactions define specificity in signal transduction.</a> Genes Dev. 14 (9), 1027-1047 (2000).</li>
<li>Rual, J. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Towards+a+proteome-scale+map+of+the+human+protein-protein+interaction+network%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Towards a proteome-scale map of the human protein-protein interaction network.</a> Nature. 437 (7062), 1173-1178 (2005).</li>
<li>Phizicky, E. M., Fields, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Protein-protein+interactions%3A+methods+for+detection+and+analysis%5BTitle%5D)+AND+%22Microbiol+Rev%22%5BJournal%5D)">Protein-protein interactions: methods for detection and analysis.</a> Microbiol Rev. 59 (1), 94-123 (1995).</li>
<li>Ho, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Systematic+identification+of+protein+complexes+in+Saccharomyces+cerevisiae+by+mass+spectrometry%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Systematic identification of protein complexes in Saccharomyces cerevisiae by mass spectrometry.</a> Nature. 415 (6868), 180-183 (2002).</li>
<li>Krogan, N. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Global+landscape+of+protein+complexes+in+the+yeast+Saccharomyces+cerevisiae%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Global landscape of protein complexes in the yeast Saccharomyces cerevisiae.</a> Nature. 440 (7084), 637-643 (2006).</li>
<li>Wittig, I., Braun, H. P., Schagger, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Blue+native+PAGE%5BTitle%5D)+AND+%22Nat+Protoc%22%5BJournal%5D)">Blue native PAGE.</a> Nat Protoc. 1 (1), 418-428 (2006).</li>
<li>Schagger, H., Cramer, W. A., von Jagow, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Analysis+of+molecular+masses+and+oligomeric+states+of+protein+complexes+by+blue+native+electrophoresis+and+isolation+of+membrane+protein+complexes+by+two-dimensional+native+electrophoresis%5BTitle%5D)+AND+%22Anal+Biochem%22%5BJournal%5D)">Analysis of molecular masses and oligomeric states of protein complexes by blue native electrophoresis and isolation of membrane protein complexes by two-dimensional native electrophoresis.</a> Anal Biochem. 217 (2), 220-230 (1994).</li>
<li>Laemmli, U. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Cleavage+of+structural+proteins+during+the+assembly+of+the+head+of+bacteriophage+T4%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Cleavage of structural proteins during the assembly of the head of bacteriophage T4.</a> Nature. 227 (5259), 680-685 (1970).</li>
<li>Beisiegel, U. <a target="_blank" href="http://onlinelibrary.wiley.com/doi/10.1002/elps.1150070102/abstract">Protein Blotting.</a> Electrophoresis. 7 (1), 1-18 (1986).</li>
<li>Killinger, B. A., Moszczynska, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Characterization+of+alpha-Synuclein+Multimer+Stoichiometry+in+Complex+Biological+Samples+by+Electrophoresis%5BTitle%5D)+AND+%22Anal+Chem%22%5BJournal%5D)">Characterization of alpha-Synuclein Multimer Stoichiometry in Complex Biological Samples by Electrophoresis.</a> Anal Chem. 88 (7), 4071-4084 (2016).</li>
<li>Newman, A. J., Selkoe, D., Dettmer, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+new+method+for+quantitative+immunoblotting+of+endogenous+alpha-synuclein%5BTitle%5D)+AND+%22PLoS+One%22%5BJournal%5D)">A new method for quantitative immunoblotting of endogenous alpha-synuclein.</a> PLoS One. 8 (11), e81314(2013).</li>
<li>Wong, S. S. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aWong%2C+SS+%22Chemistry+of+protein+conjugation+and+cross-linking%22">Chemistry of protein conjugation and cross-linking</a>. , CRC Press. Boca Raton. (1991).</li>
<li>Seddon, A. M., Curnow, P., Booth, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Membrane+proteins%2C+lipids+and+detergents%3A+not+just+a+soap+opera%5BTitle%5D)+AND+%22Biochim+Biophys+Acta%22%5BJournal%5D)">Membrane proteins, lipids and detergents: not just a soap opera.</a> Biochim Biophys Acta. 1666 (1-2), 105-117 (2004).</li>
<li>Tanford, C., Reynolds, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Characterization+of+membrane+proteins+in+detergent+solutions%5BTitle%5D)+AND+%22Biochim+Biophys+Acta%22%5BJournal%5D)">Characterization of membrane proteins in detergent solutions.</a> Biochim Biophys Acta. 457 (2), 133-170 (1976).</li>
<li>Peters, K., Richards, F. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Chemical+cross-linking%3A+reagents+and+problems+in+studies+of+membrane+structure%5BTitle%5D)+AND+%22Annu+Rev+Biochem%22%5BJournal%5D)">Chemical cross-linking: reagents and problems in studies of membrane structure.</a> Annu Rev Biochem. 46, 523-551 (1977).</li>
<li>Lomant, A. J., Fairbanks, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Chemical+probes+of+extended+biological+structures%3A+synthesis+and+properties+of+the+cleavable+protein+cross-linking+reagent+%5B35S%5Ddithiobis%28succinimidyl+propionate%29%5BTitle%5D)+AND+%22J+Mol+Biol%22%5BJournal%5D)">Chemical probes of extended biological structures: synthesis and properties of the cleavable protein cross-linking reagent [35S]dithiobis(succinimidyl propionate).</a> J Mol Biol. 104 (1), 243-261 (1976).</li>
<li>Sun, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Crystal+structure+of+mitochondrial+respiratory+membrane+protein+complex+II%5BTitle%5D)+AND+%22Cell%22%5BJournal%5D)">Crystal structure of mitochondrial respiratory membrane protein complex II.</a> Cell. 121 (7), 1043-1057 (2005).</li>
<li>Wittig, I., Schagger, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Native+electrophoretic+techniques+to+identify+protein-protein+interactions%5BTitle%5D)+AND+%22Proteomics%22%5BJournal%5D)">Native electrophoretic techniques to identify protein-protein interactions.</a> Proteomics. 9 (23), 5214-5223 (2009).</li>
</ol>

The authors have nothing to disclose.

Protein-protein interactions are important for every task living things carry out. Because of this, they are the subject of intense scrutiny and research. Multimer-PAGE is a novel method for capturing, separating, and analyzing a wide range of protein complexes. We have previously demonstrated its applicability to studying oligimerization of the disease-associated protein &#945;-synuclein11. However, it is extensible to many protein complexes, as demonstrated in Figure 2. When com...

Normal cellular function is dependent on protein-protein interactions1,2. As a result, human diseases are often marked by perturbations in the assembly and behavior of various protein complexes3. The ability to characterize such interactions is therefore critical. Current means of detecting these interactions require purification of target proteins, often followed by pull-down of their interacting partners. Conventional purification is accomplished by differential centrifugation, precipitation, and/or chromatography4. These methods are time-consuming, must be altered for each target protein, and often result in low yields. Modern purification methods involve the fusion of peptide tags to target proteins, followed by immunoprecipitation or extraction on columns loaded with beads bound to a capture molecule5,6. While this is extensible to many proteins, it requires sequence modification of the target, potentially resulting in constructs that differ in affinity for their usual binding partners. The delicate nature of some protein-protein interactions means this method may not be applicable to many scenarios. Additionally, the pull-down assays used to map protein-protein interactions may not capture an accurate cellular picture, due to restricted degrees of freedom and non-native levels of the bait protein.
Ideally, protein complexes could be detected in their native states, without the need for purification or pull-down. Blue native polyacrylamide gel electrophoresis (BN-PAGE) was developed as a less-denaturing alternative to sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and allows for the separation of some proteins and complexes from biological samples7. However, proteins in BN-PAGE separate based on a large number of variables, including size, charge, three-dimensional structure, and association with other molecules. The interactions of these factors often result in co-separation of proteins, aggregate formation, and poor protein band resolution. Two-dimensional native-polyacrylamide gel electrophoresis resolves some, but not all, of these problems8.
To circumvent the complications associated with native separation, some authors use amine-reactive cross-linking reagents, such as dithiobis(succinimidyl propionate) (DSP), to capture protein complexes in tissue lysates4. These treated lysates can then be denatured and separated by SDS-PAGE, while preserving the native size and makeup of protein complexes. However, since cross-linking reagents react based on proximity of one molecule to another, and proteins in tissue lysates have many degrees of freedom and can stochastically interact, nonspecific background cross-linking can be high, especially in concentrated samples. This can lead to difficult-to-interpret results.
Here, we demonstrate the use of a hybrid BN-PAGE/SDS-PAGE method, termed multimer-polyacrylamide gel electrophoresis (multimer-PAGE), to separate and detect protein assemblies in complex mixtures. Initially, cell lysate is suspended in polyacrylamide gel via BN-PAGE. The lysate-containing gel is then reacted with the cross-linking reagent DSP. Pseudo-immobilized and slightly separated on the gel, proteins are much less likely to react nonspecifically, meaning background cross-linker reactivity is reduced. After cross-linking, the gel bands are excised and separated via SDS-PAGE. The resultant gel can then be analyzed by any means typically associated with polyacrylamide gel electrophoresis. This method allows for the separation and detection of native protein complexes in unmodified tissue lysate, without the need for additional purification or pull-down.

<table><tbody><tr><td>&lt;strong&gt;Chemicals&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>&amp;epsilon;-Aminocaproic acid</td><td>Sigma</td><td>A2504</td><td></td></tr><tr><td>Acrylamide</td><td>Acros Organics</td><td>164855000</td><td>Toxic.</td></tr><tr><td>Acrylamide/bisacrilamide 37.5:1 (40%T stock solution)</td><td>BioRad</td><td>161-0148</td><td>Toxic.</td></tr><tr><td>Ammonium persulfate</td><td>Sigma</td><td>A3678</td><td></td></tr><tr><td>Anti rabbit IgG-HRP from goat</td><td>Santa Cruz Biotechnology</td><td>sc-2004</td><td></td></tr><tr><td>Bicinchoninic acid assay kit</td><td>Thermofisher</td><td>23225</td><td></td></tr><tr><td>Bis-tris</td><td>Sigma</td><td>B9754</td><td></td></tr><tr><td>Bovine serum albumin</td><td>Sigma</td><td>A9647</td><td></td></tr><tr><td>Butanol</td><td>Fisher Scientific</td><td>A399-1</td><td></td></tr><tr><td>Chemiluminescence substrate kit</td><td>ThermoFisher</td><td>24078</td><td></td></tr><tr><td>Coomassie blue G-250</td><td>Sigma-Aldrich</td><td>B0770</td><td></td></tr><tr><td>Digitonin</td><td>Sigma</td><td>D141</td><td>Toxic.</td></tr><tr><td>Dimethyl sulfoxide</td><td>Fisher Scientific</td><td>D128-1</td><td></td></tr><tr><td>Dithiobis(succinimidylpropionate)</td><td>Thermo Scientific</td><td>22585</td><td></td></tr><tr><td>Dry nonfat milk</td><td>LabScientific</td><td>M0841</td><td></td></tr><tr><td>Glycerol</td><td>Sigma</td><td>G9012</td><td></td></tr><tr><td>Glycine</td><td>Fisher Scientific</td><td>BP381-5</td><td></td></tr><tr><td>Halt Protease Inhibitor Cocktail</td><td>Thermofisher</td><td>78430</td><td></td></tr><tr><td>Hydrochloric acid</td><td>Fisher Scientific</td><td>A144SI-212</td><td>For titration. Caustic.</td></tr><tr><td>Methanol</td><td>Fisher Scientific</td><td>A412-4</td><td>For PVDF membrane activation. Toxic.</td></tr><tr><td>Monoclonal anti &amp;alpha;-synuclein IgG from rabbit</td><td>Santa Cruz Biotechnology</td><td>sc-7011-R</td><td></td></tr><tr><td>N,N,N&#039;,N&#039;-tetramethylethylenediamine</td><td>Sigma</td><td>T9281</td><td></td></tr><tr><td>N,N&#039;-methylenebisacrylamide</td><td>Acros Organics</td><td>16479</td><td>Toxic.</td></tr><tr><td>NP40</td><td>Boston Bioproducts</td><td>P-872</td><td></td></tr><tr><td>Polysorbate 20 (tween-20)</td><td>Fisher Scientific</td><td>BP337-500</td><td></td></tr><tr><td>Polyvinylidene fluoride transfer membranes</td><td>Thermo Scientific</td><td>88518</td><td></td></tr><tr><td>Ponceau S</td><td>Sigma</td><td>P3504</td><td></td></tr><tr><td>Potassium chloride</td><td>Fisher Scientific</td><td>P217-3</td><td></td></tr><tr><td>Potassium phosphate monobasic</td><td>Sigma</td><td>P9791</td><td></td></tr><tr><td>Protease inhibitor cocktail</td><td>Thermo Scientific</td><td>88265</td><td></td></tr><tr><td>SDS solution (10% w/v)</td><td>BioRad</td><td>161-0416</td><td></td></tr><tr><td>Sodium chloride</td><td>Fisher Scientific</td><td>BP358-212</td><td></td></tr><tr><td>Sodium dodecyl sulfate</td><td>Sigma</td><td>L37771</td><td></td></tr><tr><td>Sodium phosphate monobasic</td><td>Fisher Scientific</td><td>BP329-1</td><td></td></tr><tr><td>Tricine</td><td>Sigma</td><td>T0377</td><td></td></tr><tr><td>Tris base</td><td>Fisher Scientific</td><td>BP152-500</td><td></td></tr><tr><td>Tris-HCl (0.5 M buffer, pH 6.8)</td><td>BioRad</td><td>161-0799</td><td></td></tr><tr><td>Tris-HCl (1.5 M buffer, pH 8.8)</td><td>BioRad</td><td>161-0798</td><td></td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Instruments&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>GE Imagequant LAS 4000</td><td>GE Healthcare</td><td>28-9558-10</td><td></td></tr><tr><td>ImageJ software</td><td>NIH</td><td></td><td></td></tr><tr><td>Synergy H1 microplate reader</td><td>BioTek</td><td></td><td></td></tr><tr><td>Gel Former + Stand</td><td>Biorad</td><td></td><td></td></tr><tr><td>Microfuge 22R centrifuge</td><td>Beckman Coulter</td><td></td><td></td></tr><tr><td>2 mL dounce homogenizer</td><td></td><td></td><td></td></tr><tr><td>Vortex mixer</td><td>Fisher Scientific</td><td></td><td></td></tr><tr><td>Ultrasonic tissue homogenizer</td><td>Fisher Scientific</td><td>FB120220</td><td></td></tr></tbody></table>

multimer-page: a method for capturing and resolving protein complexes in biological samples

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

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

In this demonstration experiment, multimer-PAGE was performed on whole rat brain lysate. The resultant separated proteins were blotted onto polyvinylidene diflouride (PVDF) membranes, and then probed with antibodies against proteins that are known to form complexes. Figure 1 shows a validation of the protocol by two means. First, we demonstrate that the cross-linked proteins are cleavable by addition of a reducing agent, meaning the observed higher molecular weight specie...

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

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

The overall goal of this protocol is to enable researchers to capture, separate, and analyze native protein complexes extracted from tissue lysates using polyacrylamide gel electrophoresis. This method can aid researchers who study proteins because it is able to stabilize otherwise labile protein associations under near-native conditions, allowing for their identification and subsequent analysis. The main advantage of this technique is that it uses common biological methods so it is widely applicable and can be tailored to the goals of the individual researcher.To begin this procedure, prepare for blue native polyacrylamide gel electrophoresis as described in the text protocol. Connect the electrodes to the power supply and electrophorese the proteins in the gel at 150 volts until the dye band progresses approximately two centimeters into the resolving layer. At this point, stop and disconnect the power supply.After disassembling the electrophoresis apparatus, separate the glass panes of the gel cassette. Remove and discard the stacking layer. Carefully cut the gel just below the bottom edge of the dye front, taking care to make this cut as smooth and straight as possible.Then, dis

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Research

JoVE Journal

Biochemistry

The cell permeable crosslinker DSP [dithiobis-(succinimidyl propionate)] stabilizes transient and labile interactions in vivo, which allows their isolation using stringent protein complex purification techniques. Here we present a technique for crosslinking cells grown in culture followed by isolation of protein complexes by immunoprecipitation.

Isolation of Labile Multi-protein Complexes by in vivo Controlled Cellular Cross-Linking and Immuno-magnetic Affinity Chromatography

In this video, we describe the characterization of multiprotein complexes (MPCs) by blue native polyacrylamide gel electrophoresis (BN-PAGE). In a first dimension, dialyzed cellular lysates are separated by BN-PAGE to identify individual MPCs. In a second dimension SDS-PAGE, MPCs of interest are further subdivided to analyze their constituents by immunoblotting.

Blue Native Polyacrylamide Gel Electrophoresis (BN-PAGE) for Analysis of Multiprotein Complexes from Cellular Lysates

This video describes multimeric PAGE for separating native protein complexes from tissue homogenates. The technique is a hybrid of blue native-PAGE and SDS-PAGE techniques. The separated complexes can be characterized and studied for their role in cell functioning.

Multimer-PAGE for Separating Native Protein Complexes: A Hybrid Separation Technique Consisting of Blue Native-PAGE and SDS-PAGE to Separate Intact Multimeric Proteins From Tissue Lysate

Protein complexes catalyze key cellular functions. Detailed functional and structural characterization of many essential complexes requires recombinant production. MultiBac is a baculovirus/insect cell system particularly tailored for expressing eukaryotic proteins and their complexes. MultiBac was implemented as an open-access platform, and standard operating procedures developed to maximize its utility.

The MultiBac Protein Complex Production Platform at the EMBL

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

Protein Complex Affinity Capture from Cryomilled Mammalian Cells

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.

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

The architecture of protein complexes is essential for their function. Combining various mass spectrometric techniques proved powerful to study their assembly. We provide protocols for chemical cross-linking and native mass spectrometry and show how these complementary techniques help to elucidate the architecture of multi-subunit protein assemblies.

Combining Chemical Cross-linking and Mass Spectrometry of Intact Protein Complexes to Study the Architecture of Multi-subunit Protein Assemblies

This manuscript describes the protocol for Bimolecular Complementation Affinity Purification (BiCAP). This novel method facilitates the specific isolation and downstream proteomic characterization of any two interacting proteins, while excluding un-complexed individual proteins as well as complexes formed with competing binding partners.

Dissecting Multi-protein Signaling Complexes by Bimolecular Complementation Affinity Purification (BiCAP)

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

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

A versatile cryoslicing BN-MS protocol using a microtome is presented for high-resolution complexome profiling.

High-Resolution Complexome Profiling by Cryoslicing BN-MS Analysis

Erfahren Sie, wie Sie native Proteinkomplexe aus Gewebelysaten mit Multimer-PAGE stabilisieren und analysieren. Diese Methode ermöglicht die Erfassung labiler Proteinassoziationen unter nahezu nativen Bedingungen für die Proteomforschung.

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

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