Rap1-B is phosphorylated by protein kinase A in intact human platelets.
Agonists that increase cAMP levels in platelets promote the phosphorylation of a 24 kDa GTP-binding protein that is immunoreactive with a monoclonal antibody (M90) to the H-ras p21 protein. Evidence is presented which indicates that this protein is rap-1b, not rap1-a as previously suggested (Ohmori, T., Kikuchi, A., Yamamoto, K., Kawata, M., Kondo, J. and Takai, Y. (1988) Biochem. Biophys. Res. Commun. 157, 670-676). The amino acid sequence of labeled peptides obtained by proteolytic cleavage of the purified phosphorylated protein was identical with that of rap-1b. Furthermore, a comparison of the kinetics of phosphorylation of synthetic peptides corresponding to the C-terminal region of rap-1a and rap-1b proteins indicated that rap-1b is the preferred substrate for phosphorylation by cAMP-dependent protein kinase.
Division of Cell Biology, Burroughs Wellcome Co., Research Triangle Park, NC 27709.
W
W
Siess
D A
DA
Winegar
E G
EG
Lapetina
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology; D001792:Blood Platelets / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D001798:Blood Proteins / Q000276:immunology / Q000378:metabolism*; D011464:Epoprostenol / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D016285:Iloprost; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D020668:rap GTP-Binding Proteins
D000911:Antibodies, Monoclonal; D001798:Blood Proteins; D011464:Epoprostenol; D011494:Protein Kinases; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins; D016285:Iloprost