Name: oligopeptide competition assay for phosphorylation site determination
Uploaded: 2017-05-18T14:00:00
Description: Watch this Scientific Journal Video about Oligopeptide Competition Assay for Phosphorylation Site Determination at JoVE.com

This work was supported by the National Research Foundation of Korea grant funded by the Korean government (MSIP) (No. 2015R1A2A1A10052663 and No. 2014M1A3A3A02034698).

1. Safety
CAUTION: This protocol uses [&#947;-32P]-ATP to assess the activity of AMPK. Phosphorus-32 is a radioactive isotope, largely emitting beta radiation. Since the size of a beta particle is extremely small, it can easily penetrate clothing and skin. Both external and internal exposure to beta radiation may be harmful to human health, including by causing skin burns and tissue damage.
<ol>
	<li>Carry out all the steps that require the use of [&#947;-32P]-ATP using...

<ol>
	<li>Hardie, D. G., Schaffer, B. E., Brunet, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AMPK:+An+energy-sensing+pathway+with+multiple+inputs+and+outputs.">AMPK: An energy-sensing pathway with multiple inputs and outputs.</a> Trends Cell Biol. 26, 190-201 (2016).</li><li>Gwinn, D. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AMPK+phosphorylation+of+raptor+mediates+a+metabolic+checkpoint.">AMPK phosphorylation of raptor mediates a metabolic checkpoint.</a> Mol Cell. 30, 214-226 (2008).</li><li>Huang, H. C., Nguyen, T., Pickett, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphorylation+of+Nrf2+at+Ser-40+by+protein+kinase+C+regulates+antioxidant+response+element-mediated+transcription.">Phosphorylation of Nrf2 at Ser-40 by protein kinase C regulates antioxidant response element-mediated transcription.</a> J Biol Chem. 277, 42769-42774 (2002).</li><li>Niture, S. K., Jain, A. K., Jaiswal, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antioxidant-induced+modification+of+INrf2+cysteine+151+and+PKC-delta-mediated+phosphorylation+of+Nrf2+serine+40+are+both+required+for+stabilization+and+nuclear+translocation+of+Nrf2+and+increased+drug+resistance.">Antioxidant-induced modification of INrf2 cysteine 151 and PKC-delta-mediated phosphorylation of Nrf2 serine 40 are both required for stabilization and nuclear translocation of Nrf2 and increased drug resistance.</a> J Cell Sci. 122, 4452-4464 (2009).</li><li>Jain, A. K., Jaiswal, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GSK-3beta+acts+upstream+of+Fyn+kinase+in+regulation+of+nuclear+export+and+degradation+of+NF-E2+related+factor+2.">GSK-3beta acts upstream of Fyn kinase in regulation of nuclear export and degradation of NF-E2 related factor 2.</a> J Biol Chem. 282, 16502-16510 (2007).</li><li>Steen, H., Jebanathirajah, J. A., Rush, J., Morrice, N., Kirschner, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphorylation+analysis+by+mass+spectrometry:+myths,+facts,+and+the+consequences+for+qualitative+and+quantitative+measurements.">Phosphorylation analysis by mass spectrometry: myths, facts, and the consequences for qualitative and quantitative measurements.</a> Mol Cell Proteomics. 5, 172-181 (2006).</li><li>Dephoure, N., Gould, K. L., Gygi, S. P., Kellogg, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+and+analysis+of+phosphorylation+sites:+a+quick+guide+for+cell+biologists.">Mapping and analysis of phosphorylation sites: a quick guide for cell biologists.</a> Mol Biol Cell. 24, 535-542 (2013).</li><li>Joo, M. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AMPK+facilitates+nuclear+accumulation+of+Nrf2+by+phosphorylating+at+Serine+550.">AMPK facilitates nuclear accumulation of Nrf2 by phosphorylating at Serine 550.</a> Mol Cell Biol. 36, 1931-1942 (2016).</li><li>Sinclair, W. K., Holloway, A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Half-lives+of+some+radioactive+isotopes.">Half-lives of some radioactive isotopes.</a> Nature. 167 (4244), 365 (1951).</li><li>Chang, B. Y., Chiang, M., Cartwright, C. 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+interaction+of+Src+and+RACK1+is+enhanced+by+activation+of+protein+kinase+C+and+tyrosine+phosphorylation+of+RACK1.">The interaction of Src and RACK1 is enhanced by activation of protein kinase C and tyrosine phosphorylation of RACK1.</a> J Biol Chem. 276, 20346-20356 (2001).</li><li>Smith, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RACK1+interacts+with+filamin-A+to+regulate+plasma+membrane+levels+of+the+cystic+fibrosis+transmembrane+conductance+regulator.">RACK1 interacts with filamin-A to regulate plasma membrane levels of the cystic fibrosis transmembrane conductance regulator.</a> Am J Physiol Cell Physiol. 305 (1), C111-C120 (2013).</li></ol>

As a simple and convenient way to assess the authenticity of the predicted phosphorylation sites mediated by AMPK, here we describe an in vitro kinase assay that can be used to discover a specific phosphorylation site using competitive peptides and to verify it using a site-specific mutant. The representative data obtained from the in vitro competitive AMPK activity assay matched the results from an assay using a site-directed mutant protein, indicating that the peptide competition assay is a useful too...

Protein phosphorylation at a specific residue plays a significant role in a wide range of cellular processes. Thus, an understanding of signaling networks requires the identification of specific phosphorylation sites. In addition, the phosphorylation site determines the effect on protein function because individual domains within a protein possess different structures and functions. The activity of nuclear factor erythroid 2-related factor 2 (Nrf2), a key antioxidant transcription factor, is bi-directionally regulated through phosphorylation at different sites. Our studies have focused on the kinases that catalyze the phosphorylation of Nrf2. The stress response of Nrf2 against oxidative challenge occurs rapidly, mainly through phosphorylation at serine 40 and mediated by protein kinase C (PKC)-&#948;, which activates Nrf23,4. Conversely, Fyn catalyzes the inhibitory phosphorylation of Nrf2 at tyrosine 568 for tight control of the activity5.
The most common method used to discover phosphorylation sites is liquid chromatography/mass spectrometry (LC/MS) analysis. Rapid and highly sensitive phosphorylation site mapping data can be generated this way; however, it has several technical limitations, often generating false-negative signals. Poor sequence coverage frequently occurs in LC/MS analysis. To identify phosphorylation sites, information on the maximal amino acid coverage of a protein is required6. Proteolysis of the protein of interest with several proteases during the digestion step may be of help in improving sequence coverage. Another obstacle for the identification of phosphorylation residues is the facile loss of phosphoric acid that is frequently observed for serine- and threonine-phosphorylated peptides6,7. Labile phosphate moieties are often released from phosphopeptides during the fragmentation process7. The second option when searching for phosphorylation sites is using a peptide microarray method. It is possible to screen for the kinase target sites using a microarray chip containing peptide fragments derived from a protein of interest. However, due to the equipment requirement for the production and detection of a microarray chip, the peptide microarray method is considered time-consuming and expensive.
To overcome these challenges, an in vitro oligopeptide-competing kinase assay can be used for a protein kinase with known recognition motifs. If the consensus recognition motif of a kinase is established, putative phosphorylation sites of a candidate substrate can be predicted, and the authenticity of the sites can be validated. The most convincing method for this procedure is to show the abrogation of phosphorylation in a mutant protein in which the predicted residue is substituted with a non-phosphorylatable amino acid (i.e., serine or threonine to alanine; tyrosine to phenylalanine). However, the production and isolation of mutant proteins is time-consuming. As an alternative at the initial stage of research, the competitive peptide kinase assay is straightforward and convenient. Here, we describe a protocol for an in vitro peptide competition assay and for the validation of the phosphorylation site.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>HEPES</td>
			<td>Thermo Fisher Scientific, Waltham, MA</td>
			<td>15630</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>208337</td>
			<td></td>
		</tr>
		<tr>
			<td>EGTA</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>E3889</td>
			<td></td>
		</tr>
		<tr>
			<td>DTT</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>D9779</td>
			<td></td>
		</tr>
		<tr>
			<td>&#946;-glycerophosphate</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>G9422</td>
			<td></td>
		</tr>
		<tr>
			<td>Na3VO4</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>450243</td>
			<td></td>
		</tr>
		<tr>
			<td>Protease inhibitor cocktail</td>
			<td>Calbiochem, Nottingham, UK</td>
			<td>539134</td>
			<td></td>
		</tr>
		<tr>
			<td>ATP</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>A2383</td>
			<td></td>
		</tr>
		<tr>
			<td>AMP</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>A1752</td>
			<td></td>
		</tr>
		<tr>
			<td>AMPK</td>
			<td>Upstate Biotechnology, Lake Placid, NY</td>
			<td>14-840</td>
			<td></td>
		</tr>
		<tr>
			<td>Nrf2 (WT)</td>
			<td>Abnova, Taipei City, Taiwan</td>
			<td>H00004780-P01</td>
			<td></td>
		</tr>
		<tr>
			<td>[&#947;-32P]-ATP</td>
			<td>PerkinElmer Life and Analytical Sciences, Waltham, MA</td>
			<td>NEG502A</td>
			<td></td>
		</tr>
		<tr>
			<td>EZblue staining reagent</td>
			<td>Sigma-Aldrich, St. Louis, MO</td>
			<td>G1041</td>
			<td></td>
		</tr>
		<tr>
			<td>Pfu turbo DNA polymerase</td>
			<td>Agilent Technologies, Santa Clara, CA</td>
			<td>600250</td>
			<td></td>
		</tr>
		<tr>
			<td>dNTP mix</td>
			<td>Agilent Technologies, Santa Clara, CA</td>
			<td>200415-51</td>
			<td>Avoid multiple thaw and freezing cycle</td>
		</tr>
		<tr>
			<td>DpnI</td>
			<td>New England Biolabs, Ipswich, MA</td>
			<td>R0176S</td>
			<td></td>
		</tr>
		<tr>
			<td>LB broth</td>
			<td>Duchefa Biochemie BV, Haarlem, Netherlands</td>
			<td>L1704</td>
			<td></td>
		</tr>
		<tr>
			<td>Ampicillin</td>
			<td>Affymetrix, Santa Clara, CA</td>
			<td>11259</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose LE</td>
			<td>iNtRON Biotechnology, Sungnam, South Korea</td>
			<td>32034</td>
			<td></td>
		</tr>
		<tr>
			<td>HiYield Plus Gel/PCR DNA Mini Kit</td>
			<td>Real Biotech Corporation, Taipei, Taiwan</td>
			<td>QDF100</td>
			<td></td>
		</tr>
		<tr>
			<td>Coomassie Brilliant Blue R-250</td>
			<td>Bio-Rad Laboratories, Hercules, CA</td>
			<td>161-0400</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin</td>
			<td>Bovogen Biologicals, Victoria, Australia</td>
			<td>BSA100</td>
			<td></td>
		</tr>
		<tr>
			<td>Glutathione Sepharose 4B</td>
			<td>GE Healthcare, Marlborough, MA</td>
			<td>17-0756-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic Acid glacial</td>
			<td>Duksan pure chemicals, Ansan, South Korea</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Methyl alcohol</td>
			<td>Daejung Chemicals &#38; Metals, Siheung, South Korea</td>
			<td>5558-4410</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Typhoon FLA 7000</td>
			<td>GE Healthcare, Marlborough, MA</td>
			<td>28-9558-09</td>
			<td></td>
		</tr>
		<tr>
			<td>SDS-PAGE kit</td>
			<td>Bio-Rad Laboratories, Hercules, CA</td>
			<td>1658001FC</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum pump</td>
			<td>Bio-Rad Laboratories, Hercules, CA</td>
			<td>165-178</td>
			<td></td>
		</tr>
		<tr>
			<td>Gel dryer</td>
			<td>Bio-Rad Laboratories, Hercules, CA</td>
			<td>165-1746</td>
			<td></td>
		</tr>
		<tr>
			<td>Dancing shaker</td>
			<td>FINEPCR, Seoul, Korea</td>
			<td>CR300</td>
			<td>The machine is needed for washing step</td>
		</tr>
		<tr>
			<td>PCR machine</td>
			<td>Bio-Rad Laboratories, Hercules, CA</td>
			<td>T100</td>
			<td></td>
		</tr>
		<tr>
			<td>Incubator/shakers</td>
			<td>N-BIOTEK, GyeongGi-Do, Korea</td>
			<td>NB-205L</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcentrifuges</td>
			<td>LABOGENE, Seoul, Korea</td>
			<td>1730R</td>
			<td></td>
		</tr>
		<tr>
			<td>Chromatography columns</td>
			<td>Bio-Rad Laboratories, Hercules, CA</td>
			<td>732-1010</td>
			<td></td>
		</tr>
	</tbody>
</table>

oligopeptide competition assay for phosphorylation site determination

Protein phosphorylation at specific sites determines its conformation and interaction with other molecules. Thus, protein phosphorylation affects biological functions and characteristics of the cell. Currently, the most common method for discovering phosphorylation sites is by liquid chromatography/mass spectrometry (LC/MS) analysis, a rapid and sensitive method. However, relatively labile phosphate moieties are often released from phosphopeptides during the fragmentation step, which often yields false-negative signals. In such cases, a traditional in vitro kinase assay using site-directed mutants would be more accurate, but this method is laborious and time-consuming. Therefore, an alternative method using peptide competition may be advantageous. The consensus recognition motif of 5&#39; adenosine monophosphate-activated protein kinase (AMPK) has been established1 and was validated using a positional scanning peptide library assay2. Thus, AMPK phosphorylation sites for a novel substrate could be predicted and confirmed by the peptide competition assays. In this report, we describe the detailed steps and procedures for the in vitro oligopeptide-competing kinase assay by illustrating AMPK-mediated nuclear factor erythroid 2-related factor 2 (Nrf2) phosphorylation. To authenticate the phosphorylation site, we carried out a sequential in vitro kinase assay using a site-specific mutant. Overall, the peptide competition assay provides a method to screen multiple potential phosphorylation sites and to identify sites for validation by the phosphorylation site mutants.

Figure 1 and Figure 2 demonstrate the outcomes from repeated experiments in the previously reported paper8. Three different 10-residue oligopeptides mimicking the putative AMPK target sites (#1, 148-157 comprising Ser153; #2, 330-339 comprising Ser335; and #3, 553-562 comprising Ser558) were synthesized and used as competitors in the in vitro kinase assay. The phosphorylation of Nrf2 by AMPK was g...

Watch this Scientific Journal Video about Oligopeptide Competition Assay for Phosphorylation Site Determination at JoVE.com

Oligopeptide Competition Assay for Phosphorylation Site Determination

Peptide competition assays are widely used in a variety of molecular and immunological experiments. This paper describes a detailed method for an in vitro oligopeptide-competing kinase assay and the associated validation procedures, which may be useful to find specific phosphorylation sites.

Protein phosphorylation at specific sites determines its conformation and interaction with other molecules. Thus, protein phosphorylation affects ...

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