Description
Product Usage Information
Cells are lysed in a urea-containing buffer, cellular proteins are digested by proteases, and the resulting peptides are purified by reversed-phase solid-phase extraction. Peptides are then subjected to immunoaffinity purification using a PTMScan ® Motif Antibody conjugated to protein A agarose beads. Unbound peptides are removed through washing, and the captured PTM-containing peptides are eluted with dilute acid. Reversed-phase purification is performed on microtips to desalt and separate peptides from antibody prior to concentrating the enriched peptides for LC-MS/MS analysis. CST recommends the use of PTMScan ® IAP Buffer #9993 included in the kit.
Storage
Antibody beads supplied in IAP buffer containing 50% glycerol. Store at -20°C. Do not aliquot the antibody.
Protocol
Available protocols: PTMScan
Background
PhosphoScan Technology employs a phospho-residue (Tyr, Ser, Thr) motif antibody for phospho-peptide immunoaffinity purification from cell extracts combined with LC tandem MS/MS to identify and quantify changes in phosphorylation levels (1). Ataxia telangiectasia mutated kinase (ATM) and ataxia telangiectasia and Rad3-related kinase (ATR) are related kinases that regulate cell cycle checkpoints and DNA repair (2). The identified substrates for ATM are p53, p95/NBS1, MDM2, Chk2, BRCA1, CtIP, 4E-BP1, and Chk1 (2,3). The consensus sequence for ATM/ATR substrates is [pS/pTQ]. Hydrophobic amino acids at positions -3 and -1, and negatively charged amino acids at position +1 are positive determinants for substrate recognition by these kinases. Positively charged residues surrounding the [pS/pTQ] are negative determinants for substrate phosphorylation (4). The complex phenotype of AT cells suggests that it likely has additional substrates (4). To better understand the kinase and identify substrates for ATM and the related kinase ATR, we have developed antibodies that recognize phosphorylated serine or threonine in the [pS/pTQ] motif.
