Subunit and fine structure of the glycoprotein of bovine leukemia virus

The structure of the glycoprotein of bovine leukemia virus (BLV) was investigated. Analysis of BLV under nonreducing conditions revealed two viral glycoproteins with apparent molecular weights of 162,000 (VGP I) and 85,000 (VGP II). After reduction and alkylation, two glycosylated polypeptide chains of apparent molecular weights of 60,000 (gp 60) and 30,000 (gp 30) could be demonstrated in VGP I and VGP II; VGP I appears to contain two molecules of gp 60 and two molecules of gp 30, and VGP II consists of only one molecule of gp 60 and one molecule of gp 30 linked by disulfide bonds. Comparison of the tryptic peptides of gp 60 and gp 30 provided evidence for the existence of partial sequence relationship between gp 60 and gp 30. The structural similarity of the BLV glycoprotein molecule to immunoglobulins is discussed in regard to the possible function of this protein in the pathogenesis of bovine leukemia.