Large and small tumor antigens from simian virus 40 have identical amino termini mapping at 0.65 map units.

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Abstract
Large and small tumor (T) antigens of SV-40 were synthesized in vitro with [mouse fibroblast] L-cell extracts that had been treated by the method of Palmiter to prevent amino[NH2]-terminal acetylation of nascent proteins. Partial NH2-terminal amino acid sequences of both forms of T-antigen were determined and were identical. Methionine residues were located at positions 1 and 14, a lysine residue at position 3, and leucine residues at positions 5, 11, 13, 16, 17 and 19. These amino acid sequence data match perfectly the amino acid sequence predicted from a sequence of nucleotides in the E strand of SV-40 DNA which begins near the junction between HindII/III fragments A and C at about 0.65 map units. The sequence coding for the NH2 terminus of both proteins is probably located at this position. The data are consistent with a model for the synthesis of both forms of T-antigen that predicts that small T-antigen is coded for by a sequence of nucleotides from the 5'' end of the early region and large T-antigen is coded for by nucleotide sequences from 2 noncontiguous regions of SV-40 DNA.