Detection of a precursor-like protein of bovine leukaemia virus structural polypeptides in purified virions.

Gel filtration chromatography of disrupted bovine leukaemia virus (BLV) resulted in the isolation of the 25000 mol. wt. major internal protein (p25), two previously uncharacterized proteins of mol. wt 65000 (p65) and 12000 (p12), and a mixture of p12 and a protein of mol. wt. 15000 (p15). The p65 protein does not bind to concanavalin A and its antigenicity is ether resistant. Therefore, this polypeptide is different from the previously described glycoprotein associated with BLV. Radioimmunoprecipitation and competitive radioimmunoassays indicated that the p65 protein shares antigenic determinants with the p25, p15 and p12 proteins, respectively. Furthermore, tryptic peptide mapping demonstrated that p65 contains p25, p15, p12 and a BLV protein of mol. wt. 10000 (p10). These results are consistent with the view that p65 is the precursor of gag gene-derived core proteins of BLV.