Phosphorylation of vitronectin by a protein kinase in human plasma. Identification of a unique phosphorylation site in the heparin-binding domain

E. A. McGuire, M. E. Peacock, R. C. Inhorn, N. R. Siegel, D. M. Tollefsen

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38 Scopus citations

Abstract

Incubation of human plasma with 27 nM [γ-32P]ATP in the presence of 20 mM MnCl2 results in the phosphorylation of several proteins detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. About 60% of the incorporated radioactivity is found in a 75-kDa protein containing [32P] phosphoserine. The amino-terminal amino acid sequence of the purified 75-kDa [32P]phosphoprotein is identical to that of vitronectin (also termed serum spreading factor or complement S protein). Rabbit antiserum against vitronectin precipitates >90% of the 75-kDa [32P]phosphoprotein from plasma. Reverse phase chromatography of [32P]vitronectin degraded sequentially with CNBr and chymotrypsin yields one major labeled peptide. The sequence of the peptide, Ser-Arg-Arg-Pro-[32PO4]Ser-Arg-Ala-Thr, corresponds to residues 374-381 which are located in the heparin-binding fragment of vitronectin identified by Suzuki et al. (1984) J. Biol. Chem. 259, 15307-15314). Vitronectin could potentially be phosphorylated in vivo with ATP released from injured cells or secreted by platelets activated during hemostasis.

Original languageEnglish
Pages (from-to)1942-1945
Number of pages4
JournalJournal of Biological Chemistry
Volume263
Issue number4
StatePublished - 1988

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