Cleavage of mengovirus polyproteins in vivo.

The synthesis of mengovirus-specific proteins in vivo was studied by labeling the viral proteins with radioactive amino acids under conditions in which host protein synthesis was almost completely inhibited. Pulse-chase experiments enabled the kinetic analysis of the cleavages of certain viral protein precursors and the formation of others. The pattern of cleavages of mengovirus precursor polypeptides is similar to that of encephalomyocarditis virus. The major difference between the two viruses seems to be in the molar concentration in which the various primary products are produced. The molar ratio of the A protein, which is the precursor of the capsid proteins, to that of the primary products F and C, is approximately 1.5 to 2.0: 1: 1. Possible explanations for the unequal appearance of the structural and nonstructural proteins are discussed.