[Small GTP-binding protein and platelet function].
In platelets, nearly ten small GTP-binding proteins (G proteins) are identified. Among these small G proteins, smg p21 is the most abundant. The C terminus of smg p21 is processed by three post-translational modifications: geranylgeranylation, removal of three amino acids and carboxyl methylation. There are two regulatory proteins for smg p21, smg p21 GTPase activating protein (GAP) and smg GDP dissociation stimulator (GDS). Moreover, smg p21 is phosphorylated by A-Kinase and this phosphorylation stimulates the action of smg GDS. C-Kinase and Ca2+ induce platelet activation, while A-Kinase antagonizes this activation. Since smg p21 is the substrate of A-Kinase, it is possible that smg p21 mediates the A-Kinase action and inhibits the platelet function, such as aggregation and secretion. The mode of action of and the possible function of smg p21 in platelets are discussed.
Kawata
M
M
Department of Biochemistry, Kobe University School of Medicine.
Takai
Y
Y
D019883:Alkyl and Aryl Transferases; D000818:Animals; D001792:Blood Platelets / Q000502:physiology*; D002118:Calcium / Q000378:metabolism / Q000502:physiology; D019204:GTP-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D020690:GTPase-Activating Proteins; D006801:Humans; D008970:Molecular Weight; D010766:Phosphorylation; D010974:Platelet Aggregation; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000502:physiology; D015398:Signal Transduction; D014166:Transferases / Q000302:isolation & purification
D020690:GTPase-Activating Proteins; D011506:Proteins; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C068462:rhoA p21 geranylgeranyltransferase; D019204:GTP-Binding Proteins; D002118:Calcium