Portal de Periódicos da CAPES

Rap1-b is phosphorylated by protein kinase a in intact human platelets

1990; Elsevier BV; Volume: 170; Issue: 2 Linguagem: Inglês

10.1016/0006-291x(90)92182-y

1090-2104

Wolfgang Siess, Deborah A. Winegar, E G Lapetina,

Coagulation, Bradykinin, Polyphosphates, and Angioedema

Agonists that increase cAMP levels in platelets promote the phosphorylation of a 24 kDa GTP-bindng 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.