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

Authors
Journal
Biochemical and Biophysical Research Communications
0006-291X
Publisher
Elsevier
Publication Date
Volume
170
Issue
2
Identifiers
DOI: 10.1016/0006-291x(90)92182-y
Disciplines
  • Biology

Abstract

Abstract 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.

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