The Polypeptide Composition of the Encephalomyocarditis Virus Particle

SUMMARY The encephalomyocarditis (EMC) virus particle appears to contain about 60 chains each of four major polypeptides and 2 chains of a minor component. Two major polypeptides were assumed to have the same mol. wt. of 32000 since they were not separated by electrophoresis on polyacrylamide gels containing SDS, although they are separable by calcium phosphate chromatography. The two other major polypeptides appeared to be homogeneous when examined by calcium phosphate chromatography; they have mol. wt. of 25000 and 11000, based upon gel electrophoresis, although examination of the latter polypeptide by gel filtration in the presence of 6 m-guanidine gave a mol. wt. of 6700. The minor component has a mol. wt., determined by gel electrophoresis, of about 42000. Similar results were obtained for the closely related Mouse-Elberfeld (ME) virus except that two polypeptides of mol. wt. 33000 and 30800, were found rather than two of 32000. Since the ME and EMC viruses studied were both grown in Krebs II ascites tumour cells, the differences in mol. wt. of the polypeptides probably reflected differences either in the specificity of the cleavage enzyme or in the amino acid sequence in the cleavage region.