Antibodies specific for the carboxy- and amino-terminal regions of simian virus 40 large tumor antigen.

Antibodies specific for the amino- and carboxy-terminal portions of simian virus 40 large tumor (T) antigen were obtained by immunization of rabbits with synthetic peptides corresponding to these regions. The amino-terminal synthetic peptide has the sequence Ac-Met-Asp-Lys-Val-Leu-Asn-Arg-(Tyr). The tyrosine residue was introduced in order to couple the peptide to bovine serum albumin with bis-diazotized benzidine. The carboxy-terminal peptide has the sequence Lys-Pro-Pro-Thr-Pro-Pro-Pro-Glu-Pro-Glu-Thr. It was coupled to bovine serum albumin with glutaraldehyde. The antisera against both peptides reacted with large T antigen. The specificity of the immune reaction was demonstrated by inhibition experiments using excess synthetic peptides. Furthermore, fragments of T antigen encoded by the nondefective adenovirus 2-simian virus 40 hybrid viruses Ad2+ND2 and Ad2+ND4, which contain the carboxy terminus and lack the amino terminus of large T antigen, were precipitated only with antiserum to the carboxy-terminal peptide. Small T antigen was not precipitated with either serum, suggesting that the amino terminus of small T antigen has a conformation different from that of large T antigen or that it is sterically hindered by a host protein. The procedures used here are of general importance for identification and characterization of gene product.