Guanidine-resistant mutants of aphthovirus induce the synthesis of an altered nonstructural polypeptide, P34.

Extracts of cells infected with guanidine-resistant mutants of aphthovirus were examined for differences in virus-induced polypeptides by using electrofocusing. Four of 1 independent spontaneous mutants induced the synthesis of an altered nonstructural polypeptide, P34. The precursor of P34, P52, and a previously unmapped polypeptide, P20c, also carried these charge-change mutations. No mutations in other regions of the genome were detected, and the remaining six guanidine-resistant mutants appeared entirely normal by electrofocusing. However, when the P34 of one of the latter mutants was examined by tryptic peptide fingerprinting, it too differed from that of the guanidine-sensitive parent. The frequency of P34 alterations among guanidine-resistant mutants suggests that P34 is functionally involved in the antiviral action of guanidine.