Phosphorylation of vitronectin by a protein kinase in human plasma. Identification of a unique phosphorylation site in the heparin-binding domain.
Incubation of human plasma with 27 nM [gamma-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 greater than 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.
D001665:Binding Sites; D001798:Blood Proteins / Q000378:metabolism; D006023:Glycoproteins / Q000097:blood*; D006493:Heparin / Q000378:metabolism*; D006801:Humans; D010449:Peptide Mapping; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D011494:Protein Kinases / Q000097:blood*; D019096:Vitronectin
D001798:Blood Proteins; D006023:Glycoproteins; D019096:Vitronectin; D010768:Phosphoserine; D006493:Heparin; D011494:Protein Kinases