RAP1B, Member Of RAS Oncogene Family (RAP1B)

The deduced 184-amino acid protein is 95% identical to RAP1A. RAP1B shares several properties with the RAS protein, suggesting that it may bind GTP/GDP and have a membrane location.RAP1B is mainly located at the membrane, but translocates to the cytosol upon activation. In activated platelets, RAP1B interacts with the reorganized actin-based cytoskeleton. RAP1B is activated by phosphorylation, increased intracellular Ca(2+), and by agonist-induced stimulation of Gi, which results in the rapid binding of GTP to RAP1B. RAP1B is posttranslationally modified by the geranylgeranylation of cys181. Further modifications cause proteolytic removal of the last 3 C-terminal amino acids, followed by partial methylation of the remaining terminal cysteinyl carboxyl group.