Tyrosine-specific phosphorylation of gpIIIa in platelet membranes.
In vitro phosphorylation of platelet subcellular fractions revealed that most of the alkali-resistant phosphoproteins and the majority of pp60c-src were in the surface membrane fraction. An alkali-resistant phosphoprotein of about 100 kDa was also immune precipitated by an anti-phosphotyrosine antibody and comigrated with gpIIIa. The phosphorylation of gpIIIa, but not gpIIb, was confirmed by the comparison of reduced and non-reduced gels, and this protein was phosphorylated exclusively on tyrosine. In contrast, both gpIIb and gpIIIa were phosphorylated when the purified complex was added to immunopurified, immobilised pp60c-src. A synthetic peptide with partial homology to a putative tyrosine phosphorylation site in the cytoplasmic domain of gpIIIa was phosphorylated by antibody-purified pp60c-src. Our results indicate that tyrosine-specific phosphorylation of gpIIIa by pp60c-src may play a role in the regulation of platelet function.
Elmore
M A
MA
Department of Biochemistry and Cell Biology, Hunterian Institute, Royal College of Surgeons of England, London.
Anand
R
R
Horvath
A R
AR
Kellie
S
S
D000596:Amino Acids / Q000302:isolation & purification; D001792:Blood Platelets / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008970:Molecular Weight; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism; D010766:Phosphorylation; D010980:Platelet Membrane Glycoproteins / Q000302:isolation & purification / Q000378:metabolism*; D014443:Tyrosine
D000596:Amino Acids; D010980:Platelet Membrane Glycoproteins; D014443:Tyrosine; D015688:Oncogene Protein pp60(v-src)