AF was supported by a starting grant from the European Research Council under the European Community&#39;s Seventh Framework Programme (FP7/2007-2013) / ERC Grant agreement n&#176; 203413 and by the Minerva Center for Bio-hybrid complex systems.HA and AI are supported by the Dalia and Dan Maydan Fellowship for advanced degree students at the Hebrew University of Jerusalem.

1. Designing a Peptide Array
<ol>
	<li>Divide the sequence of the target protein into partly overlapping 10-20 residues peptides. Vary the amount of overlap on the specific experiment and the resources of the performing lab, but in principle the longer the overlap the better. When designing the peptides take into account known secondary structure elements in the protein that can be responsible for the interaction.</li>
	<li>Order the designed peptide array through commercial vendors. Here, use peptides covalently bound...

<ol>
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B., Buus, S., Schafer-Nielsen, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+Mapping+of+Linear+Antibody+Epitopes+in+Human+Serum+Albumin+Using+High-Density+Peptide+Arrays.">Identification and Mapping of Linear Antibody Epitopes in Human Serum Albumin Using High-Density Peptide Arrays.</a> PLoS ONE. 8 (7), (2013).</li><li>Uecker, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+substrate+peptide+for+the+FLT3+receptor+tyrosine+kinase.">A substrate peptide for the FLT3 receptor tyrosine kinase.</a> British Journal of Haematology. 144 (1), 127-130 (2009).</li><li>Gabizon, R., Faust, O., Benyamini, H., Nir, S., Loyter, A., Friedler, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure-activity+relationship+studies+using+peptide+arrays:+the+example+of+HIV-1+Rev-integrase+interaction.">Structure-activity relationship studies using peptide arrays: the example of HIV-1 Rev-integrase interaction.</a> Med. Chem. Commun. 4 (1), 252-259 (2013).</li><li>Frank, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+SPOT-synthesis+technique:+Synthetic+peptide+arrays+on+membrane+supports&#8212;principles+and+applications.">The SPOT-synthesis technique: Synthetic peptide arrays on membrane supports&#8212;principles and applications.</a> Journal of Immunological Methods. 267 (1), 13-26 (2002).</li><li>Falsey, J. R., Renil, M., Park, S., Li, S., Lam, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Peptide+and+Small+Molecule+Microarray+for+High+Throughput+Cell+Adhesion+and+Functional+Assays.">Peptide and Small Molecule Microarray for High Throughput Cell Adhesion and Functional Assays.</a> Bioconjugate Chemistry. 12 (3), 346-353 (2001).</li><li>Castiel, A., Danieli, M. 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Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+human+microcephaly+protein+STIL+interacts+with+CPAP+and+is+required+for+procentriole+formation.">The human microcephaly protein STIL interacts with CPAP and is required for procentriole formation.</a> Embo J. 30 (23), 4790-4804 (2011).</li><li>Vulprecht, J., David, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=STIL+is+required+for+centriole+duplication+in+human+cells.">STIL is required for centriole duplication in human cells.</a> Journal of Cell Science. 125 (5), 1353-1362 (2012).</li><li>Campaner, S., Kaldis, P., Izraeli, S., Kirsch, I. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sil+phosphorylation+in+a+Pin1+binding+domain+affects+the+duration+of+the+spindle+checkpoint.">Sil phosphorylation in a Pin1 binding domain affects the duration of the spindle checkpoint.</a> Mol Cell Biol. 25 (15), 6660-6672 (2005).</li><li>Kasai, K., Inaguma, S., Yoneyama, A., Yoshikawa, K., Ikeda, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SCL/TAL1+interrupting+locus+derepresses+GLI1+from+the+negative+control+of+suppressor-of-fused+in+pancreatic+cancer+cell.">SCL/TAL1 interrupting locus derepresses GLI1 from the negative control of suppressor-of-fused in pancreatic cancer cell.</a> Cancer Res. 68 (19), 7723-7729 (2008).</li><li>Chaturvedi, P., Sudakin, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chfr+regulates+a+mitotic+stress+pathway+through+its+RING-finger+domain+with+ubiquitin+ligase+activity.">Chfr regulates a mitotic stress pathway through its RING-finger domain with ubiquitin ligase activity.</a> Cancer Res. 62 (6), 1797-1801 (2002).</li><li>Olaussen, K. a., Commo, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synergistic+proapoptotic+effects+of+the+two+tyrosine+kinase+inhibitors+pazopanib+and+lapatinib+on+multiple+carcinoma+cell+lines.">Synergistic proapoptotic effects of the two tyrosine kinase inhibitors pazopanib and lapatinib on multiple carcinoma cell lines.</a> Oncogene. 28 (48), 4249-4260 (2009).</li><li>Reingewertz, T. H., Britan-Rosich, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+the+Vif&#8211;A3G+interaction+using+peptide+arrays:+A+basis+for+anti-HIV+lead+peptides.">Mapping the Vif&#8211;A3G interaction using peptide arrays: A basis for anti-HIV lead peptides.</a> Bioorganic &amp; Medicinal Chemistry. 21 (12), 3523-3532 (2013).</li><li>Katz, C., Benyamini, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+basis+of+the+interaction+between+the+antiapoptotic+Bcl-2+family+proteins+and+the+proapoptotic+protein+ASPP2.">Molecular basis of the interaction between the antiapoptotic Bcl-2 family proteins and the proapoptotic protein ASPP2.</a> Proc Natl Acad Sci U S A. 105 (34), 12277-12282 (2008).</li><li>Katz, C., Zaltsman-Amir, Y., Mostizky, Y., Kollet, N., Gross, A., Friedler, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+Basis+of+the+Interaction+between+Proapoptotic+Truncated+BID+(tBID)+Protein+and+Mitochondrial+Carrier+Homologue+2+(MTCH2)+Protein:+KEY+PLAYERS+IN+MITOCHONDRIAL+DEATH+PATHWAY.">Molecular Basis of the Interaction between Proapoptotic Truncated BID (tBID) Protein and Mitochondrial Carrier Homologue 2 (MTCH2) Protein: KEY PLAYERS IN MITOCHONDRIAL DEATH PATHWAY.</a> Journal of Biological Chemistry. 287 (18), 15016-15023 (2012).</li><li>Rosenberg, M. 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Peptide array screening is an excellent tool for identifying the binding sites of a target protein in its partners. This assay is fast and easy to perform and the results can be obtained in one or two working days. Peptide array screening is versatile and can be used for many purposes. It can be used for characterizing post translation modifications such as phosphorylation and identifying substrates of kinases. For example: the FLT3 kinase, which is related to acute myeloid leukemia, phosphorylates Tyr-containing substra...

Protein-protein interactions mediate most of the processes in the living cell. Impaired protein interactions may result in disease, making protein interactions important drug targets. It is thus highly important to understand these interactions at the molecular level. Protein interactions are studied using a variety of techniques ranging from cellular and biochemical assays to quantitative biophysical assays, and these may be performed either with full-length proteins, with protein domains or with peptides. Peptides serve as excellent tools to study protein interactions. This is because peptides can be easily synthesized and allow the focusing on a specific interaction site on one hand and on multiple protein targets in a high throughput manner on the other hand1,2. Peptide array screening is a fast, easy to perform method for obtaining a large amount of data about the interactions of a target protein with numerous partners in a short time3. Unlike other biochemical or biophysical methods for detecting and analyzing protein-protein interactions, peptide array screening requires a very low concentration of protein and can detect very weak binding. Peptide arrays can be used for many applications in peptide-protein interactions such as mapping of protein-protein or receptor-ligand interaction sites4, homo- or hetero-oligomerization interfaces, characterizing antibodies epitopes5, studying enzyme activities6 and high throughput structure-activity relationship (SAR) studies7. For an in-depth review about peptide array screening see Katz et al. 4
Several types of peptide arrays currently exist. There are two major synthetic strategies for making peptide arrays: synthesis of the peptides before attaching them to the solid support, or synthesis of peptides directly on the solid support, mainly using the SPOT technique4,8. The peptides are synthesized on the solid support usually by 9-fluorenylmethyloxycarbonyl (Fmoc) chemistry8. Among the common synthetic schemes are peptide attachment through the N terminus (e.g., JPT pepstar arrays9) and peptide attachment through the C terminus (e.g., PEPSCAN pepchip arrays10, JPT pepspot arrays9 and INTAVIS celluspot arrays11)4. The solid support can vary and so does the chemistry of the peptide coupling to it. Cys-terminated peptides can be attached to glass slides via the thiol group12. The N terminus of a peptide can be covalently bound to a hydroxyl group on the cellulose membrane through esterification of the amino acid attached8.
Here we present a detailed protocol for screening peptide arrays as a method for studying protein-protein interactions. The array we used is the Celluspots array, which is a micro-array containing large amount of spots (duplicates of up to 384 spots) on a small cellulose membrane supported by a glass slide. This enables working with low volumes of protein and antibodies and obtaining significant amount of data per single experiment. This array also contains high peptide density that allows detection of low affinity binding. The array was used for mapping the STIL-CHFR interaction, which is highly important for controlling normal cell proliferation13. Uncontrolled interaction between the two proteins can lead to the development of cancer. By mapping this interaction we found the specific binding site and binding residues14. This paves the way for designing rational inhibitors that inhibit this protein-protein interaction.

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			<td height="21" style="height:21px;width:231px;">Name of Reagent/ Equipment</td>
			<td style="width:231px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:167px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Peptide array</td>
			<td>INTAVIS Bioanalytical Instruments</td>
			<td></td>
			<td></td>
		</tr>
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			<td height="21" style="height:21px;">His-probe Antibody (H-3) HRP</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-8036 HRP</td>
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			<td height="21" style="height:21px;">EZ-ECL Kit</td>
			<td>Biological industries</td>
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			<td height="21" style="height:21px;">Skim Milk</td>
			<td>Becton, Dickinson and Company</td>
			<td style="width:119px;">232100</td>
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			<td height="21" style="height:21px;">LAS-3000 camera&#160;</td>
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identifying protein-protein interaction sites using peptide arrays

Protein-protein interactions mediate most of the processes in the living cell and control homeostasis of the organism. Impaired protein interactions may result in disease, making protein interactions important drug targets. It is thus highly important to understand these interactions at the molecular level. Protein interactions are studied using a variety of techniques ranging from cellular and biochemical assays to quantitative biophysical assays, and these may be performed either with full-length proteins, with protein domains or with peptides. Peptides serve as excellent tools to study protein interactions since peptides can be easily synthesized and allow the focusing on specific interaction sites. Peptide arrays enable the identification of the interaction sites between two proteins as well as screening for peptides that bind the target protein for therapeutic purposes. They also allow high throughput SAR studies. For identification of binding sites, a typical peptide array usually contains partly overlapping 10-20 residues peptides derived from the full sequences of one or more partner proteins of the desired target protein. Screening the array for binding the target protein reveals the binding peptides, corresponding to the binding sites in the partner proteins, in an easy and fast method using only small amount of protein.
In this article we describe a protocol for screening peptide arrays for mapping the interaction sites between a target protein and its partners. The peptide array is designed based on the sequences of the partner proteins taking into account their secondary structures. The arrays used in this protocol were Celluspots arrays prepared by INTAVIS Bioanalytical Instruments. The array is blocked to prevent unspecific binding and then incubated with the studied protein. Detection using an antibody reveals the binding peptides corresponding to the specific interaction sites between the proteins.

STIL is a highly important centrosomal protein. It controls normal cell division and cell proliferation13,15&#8211;19. STIL interacts with several proteins 18,20,21, and most of the interactions occur through its central part, which is an intrinsically disordered region (IDR)14. We designed an array composed of peptides derived from the STIL binding protein CHFR. CHFR is a tumor suppressor that is induced in response to mitotic stress22. Since the structur...

Watch this Scientific Journal Video about Identifying Protein-protein Interaction Sites Using Peptide Arrays at JoVE.com

Identifying Protein-protein Interaction Sites Using Peptide Arrays

Peptide array screening is a high throughput assay for identifying protein-protein interaction sites. This allows mapping multiple interactions of a target protein and can serve as a method for identifying sites for inhibitors that target a protein. Here we describe a protocol for screening and analyzing peptide arrays.

Protein-protein interactions mediate most of the processes in the living cell and control homeostasis of the organism. Impaired protein interactions may ...

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17.8K visualizações.  The Hebrew University of Jerusalem. Peptide array screening is a high throughput assay for identifying protein-protein interaction sites. This allows mapping multiple interactions of a target protein and can serve as a method for identifying sites for inhibitors that target a protein. Here we describe a protocol for screening and analyzing peptide arrays.