Bovine Coronavirus Structural Proteins

The tissue culture-adapted strain (Mebus) of bovine coronavirus was grown in the presence of isotopically labeled amino acids, glucosamine, or orthophosphate for the purpose of analyzing the virion structural proteins. Five species of polypeptides were identified when purified virions were solubilized in urea and sodium dodecyl sulfate and resolved by polyacrylamide gel electrophoresis. Four species were glycosylated and had apparent molecular weights of 140,000, 120,000, 100,000, and 26,000. The glycoproteins were susceptible to proteolytic cleavage and enzymatic iodination when intact virions were studied and are thus at least partially external to the virion envelope. The 140,000-molecular-weight glycoprotein is apparently a dimer of 65,000-molecular-weight glycopolypeptides held together by disulfide linkages. Species 5 was phosphorylated and had an apparent molecular weight of 52,000. In the intact virion, it was unaffected by protease and was not enzymatically iodinated. It is therefore apparently an internal protein.