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Identification of protein tyrosine phosphatase 1B and casein as substrates for 124-v-Mos

Record type: Article

Background The mos proto-oncogene encodes a cytoplasmic serine/threonine-specific protein kinase with crucial function during meiotic cell division in vertebrates. Based on oncogenic amino acid substitutions the viral derivative, 124-v-Mos, displays constitutive protein kinase activity and functions independent of unknown upstream effectors of mos protein kinase. We have utilized this property of 124-v-Mos and screened for novel mos substrates in immunocomplex kinase assays in vitro.
Results We generated recombinant 124-v-Mos using the baculovirus expression system in Spodoptera frugiperda cells and demonstrated constitutive kinase activity by the ability of 124-v-Mos to auto-phosphorylate and to phosphorylate vimentin, a known substrate of c-Mos. Using this approach we analyzed a panel of acidic and basic substrates in immunocomplex protein kinase assays and identified novel in vitro substrates for 124-v-Mos, the protein tyrosine phosphatase 1B (PTP1B), alpha-casein and beta-casein. We controlled mos-specific phosphorylation of PTP1B and casein in comparative assays using a synthetic kinase-inactive 124-v-Mos mutant and further, tryptic digests of mos-phosphorylated beta-casein identified a phosphopeptide specifically targeted by wild-type 124-v-Mos. Two-dimensional phosphoamino acid analyses showed that 124-v-mos targets serine and threonine residues for phosphorylation in casein at a 1:1 ratio but auto-phosphorylation occurs predominantly on serine residues.
Conclusion The mos substrates identified in this study represent a basis to approach the identification of the mos-consensus phosphorylation motif, important for the development of specific inhibitors of the Mos protein kinase.

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Citation

Proikas-Cezanne, Tassula, Stabel, Silvia and Riethmacher, Dieter (2002) Identification of protein tyrosine phosphatase 1B and casein as substrates for 124-v-Mos BMC Biochemistry, 3, (6), pp. 1-7. (doi:10.1186/1471-2091-3-6).

More information

Published date: 4 April 2002
Keywords: cell line, non-receptor type 1, caseins, in vitro, proto-oncogene proteins c-mos, threonine, phosphorylation, protein-serine-threonine kinases, protein tyrosine phosphatase, genetics

Identifiers

Local EPrints ID: 60137
URI: http://eprints.soton.ac.uk/id/eprint/60137
ISSN: 1471-2091
PURE UUID: 63d6822d-decb-4e2c-a8c8-ab63d8fbcd1f

Catalogue record

Date deposited: 08 Sep 2008
Last modified: 17 Jul 2017 14:23

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