Binding of pp60v-src to membranes: evidence for multiple membrane interactions

Membrane association of pp60v-src, the myristylated transforming protein of Rous sarcoma virus, has been shown to be a receptor-mediated process, which is inhibited by myristylated src peptides containing the N-terminal 11 amino acids of the v-src sequence (MGYsrc). By cross-linking radiolabelled MGYsrc peptide to fibroblast membranes, a 32-kilodalton membrane protein was identified as a candidate src receptor. To elucidate the potential role of p32 in binding pp60v-src, we studied the relationship between binding of MGYsrc peptide and pp60v-src polypeptide to cellular membranes. The subcellular membrane distribution of p32 was distinct from that of pp60v-src in transformed cells. Moreover, under certain defined in vitro conditions, it was possible to inhibit peptide cross-linking to p32 without significantly affecting pp60v-src membrane binding. However, when internal sequences were removed from pp60v-src, the binding characteristics of the src deletion polypeptide and MGYsrc peptide became identical. These data indicate that the presence of internal membrane binding domains influences the interaction of myristylated N-terminal src sequences with p32, and suggest that accessory binding factors might be involved in establishing stable contact between pp60v-src and the membrane phospholipid bilayer.