Antiserum specific for the carboxy terminus of the transforming protein of Rous sarcoma virus.

An antiserum specific for the carboxy terminus of p60src, the transforming protein of Rous sarcoma virus, was produced by immunization of rabbits with a conjugate of bovine serum albumin and the synthetic peptide NH2-Tyr-Val-Leu-Glu-Val-Ala-Glu-COOH. The carboxy-terminal six amino acids of this peptide correspond in sequence to that deduced for the carboxy terminus of the p60src of the Schmidt-Ruppin strain of Rous sarcoma virus of subgroup A. The p60src proteins of the several strains of Rous sarcoma virus and the cellular homolog of the viral transforming protein, p60c-src, comprise a polymorphic family of polypeptides. The anticarboxy-terminal serum reacted readily with the p60src proteins of three different strains of Rous sarcoma virus. In contrast, no precipitation of cellular p60c-src could be detected with this serum. This suggests that the viral p60src proteins have identical carboxy termini and that the carboxy terminus of cellular p60c-src may be different from that of viral p60src. The anticarboxy-terminal serum reacted poorly with the subpopulation of viral p60src which is present in a complex with two cellular phosphoproteins. Apparently, the presence of the two cellular proteins interferes with the recognition of p60src by the anticarboxy-terminal serum. It seems likely, therefore, that these two cellular proteins bind to the carboxy-terminal domain of p60src.