Relationship of polypeptide products of the transforming gene of Rous sarcoma virus and the homologous gene of vertebrates

Abstract

All vertebrate cells contained a gene, sarc, that has some homology with the transforming gene of Rous sarcoma virus, src. The polypeptide products of the sarc gene, p60sarc, of human, mouse and chicken cells were compared with the polymorphic polypeptide product of the src gene, p60src, of several strains of Rous sarcoma virus by 2-dimensional peptide mapping. p60sarc from chicken cells was clearly related to every viral p60src. Eleven of its 13 methionine-containing tryptic peptides were present in some viral p60src. Conversely, the other 2 peptides were not present in any p60src examined so far. The 11 peptides from p60sarc of chickens that were shared with viral p60src were not all present in any single viral p60src. These 11 peptides most closely resemble those in the p60srcs of B77 virus and the Prague strain of Rous sarcoma virus. These data are consistent with the hypothesis that cellular sarc is the progenitor of viral src. The p60sarc of human, mouse and chicken cells were so similar in tryptic peptide composition that they were more closely related to each other than were some viral p60src. The 2 mammalian p60sarc differed from avian p60sarc most notably in that they lacked a peptide that chicken p60sarc shares with all the viral p60src. The similarity of these maps suggests that the sequence of the p60sarc polypeptide diverged very little during evolution. This may imply that p60sarc is an essential cellular component.