Peptide analysis of the transformation-specific antigen from avian sarcoma virus-transformed cells

Abstract

Sera from rabbits bearing tumors induced by avian sarcoma virus (ASV) were used to immunoprecipitate virus-specific proteins from extracts of chicken, hamster and field vole cells transformed by ASV. Two virus-specific proteins having MW of 76,000 and 60,000 were found in all cell lines examined. The 76,000 MW protein, Pr76, is the precursor to the internal core proteins of ASV. The 60,000 MW (60K) transformation-specific antigen from each cell line was subjected to peptide analysis, using chymotrypsin and Staphylococcus aureus V8 protease. The resulting peptide maps of the 60K [kilodalton] protein from the different ASV-infected cell types were similar for each enzyme, strongly suggesting that the 60K protein is virus coded. Two-dimensional analysis of chymotryptic peptides from Pr76 and 60K reveals that 60K is not related to the gs antigen precursor. Radiolabeling of ASV-transformed cells with inorganic phosphate revealed that 60K is phosphorylated in vivo. The 60K proteins isolated from both ASV-transformed chicken and field vole cells contained 1 tryptic phosphopeptide. The tryptic phosphopeptides of 60K from both cell lines migrated identically upon 2-dimensional peptide analyses, and their migration differed from that of the principal phosphopeptide of Pr76.