Common methionine-tryptic peptides near the amino-terminal end of primate papovavirus tumor antigens.

The tumor antigens directed by human papovaviruses BK and JC and the monkey papovavirus simian virus 40 have two methionine-containing tryptic peptides in common. These peptides are constituents of the small forms of papovavirus tumor antigen (17,000 daltons) which are present in lytically infected and transformed cells and which are believed to share some amino acid sequences with the amino-terminal portion of the larger tumor antigen species (97,000 daltons). In addition to the two peptides, which are present in all three papovavirus tumor antigens, the larger forms of the tumor antigens specified by simian virus 40 and BK virus share four other methionine-containing tryptic peptides, two of which are also present in the smaller (17,000 daltons) species of antigen. The occurrence of common peptides at the amino-terminal portion of tumor antigens of primate papovaviruses suggests that these conserved regions may play a fundamental role in the function of these proteins and in the propagation of these viruses in nature. The tryptic peptides of the small forms of papovavirus tumor antigen were examined and compared to those present in the large species. Out of a total of nine and ten methionine-containing peptides in the 17,000-dalton tumor antigens of simian virus 40 and BK virus, seven and nine peptides, respectively, are constituents of the corresponding larger (97,000 daltons) forms of the antigen.