Implications of the picornavirus capsid structure for polyprotein processing.

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Abstract
Mature picornaviral proteins are derived by progressive, posstranslational cleavage of a precursor polyprotein. These cleavages play a role in the control of virus functions. Although the processed termini are separated by as much as 75 .ANG. in the native virus capsid, the fold and arrangement fof polypeptide chains in a promoter before proteolysis are likely to be similar to that found in the mature virus. The three-dimensional structures of rhinovirus and Mengo virus suggest that the cleavage sites within the protmeric precursor are in structurally flexible regions. The final proteolytic processing event, maturation of the virion peptide vPO (also called peptide 1AB) appears to occur by an unusual autocalytic serine protease-type mechanism possibly involving viral RNA basic groups that would serve as proton-abstractors during the cleavage reaction.