ASSOCIATION OF ELONGATION-FACTOR 1-ALPHA AND RIBOSOMAL-PROTEIN-13 WITH THE PROLINE-RICH REGION OF YEAST ADENYLYL CYCLASE-ASSOCIATED PROTEINCAP

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, CA P possesses two proline-rich segments, P-1 and P-2, resembling a conse nsus sequence for binding SH3 domains, We have identified two yeast pr oteins with molecular sizes of 48 and 46 kDa associated specifically w ith P-2. Determination of partial protein sequences demonstrated that the 48-kDa and 46-kDa proteins correspond to EF1 alpha and rL3, respec tively, neither of which contains any SH3-domain-like sequence. Deleti on of P-2 from CAP resulted in loss of the activity to bind the two pr oteins either in vivo or in vitro. Yeast cells whose chromosomal CAP w as replaced by the P-2-deletion mutant displayed an abnormal phenotype represented by dissociated localizations of CAP and F-actin, which we re colocalized in wild-type cells. These results suggest that these as sociations may have functional significance. (C) 1997 Academic Press.