Association of elongation factor 1 alpha and ribosomal protein 13 with the proline-rich region of yeast adenylyl cyclase-associated protein CAP

CAP is a multifunctional protein; the N-terminal region binds adenylyl cyclase and controls its response to Ras while the C-terminal region is involved in cytoskeletal regulation. In between the two regions, CAP possesses two proline-rich segments, P-1 and P-2, resembling a consensus sequence for binding SH3 domains, We have identified two yeast proteins with molecular sizes of 48 and 46 kDa associated specifically with P-2. Determination of partial protein sequences demonstrated that the 48-kDa and 46-kDa proteins correspond to EF1 alpha and rL3, respectively, neither of which contains any SH3-domain-like sequence. Deletion of P-2 from CAP resulted in loss of the activity to bind the two proteins either in vivo or in vitro. Yeast cells whose chromosomal CAP was replaced by the P-2-deletion mutant displayed an abnormal phenotype represented by dissociated localizations of CAP and F-actin, which were colocalized in wild-type cells. These results suggest that these associations may have functional significance. (C) 1997 Academic Press.