Autoproteolytic cleavage of recombinant 3C proteinase of hepatitis A virus.

A hepatitis A virus cDNA fragment coding for the viral proteinase 3C was expressed as a chimeric protein fused in-frame to the C-terminus of beta-galactosidase. Following induction of the lac Z promoter, polypeptides of 150, 28, 26, and 16 kDa, all of which carry 3C antigenicity, were produced. The 28- and 26-kDa proteins were identified as autoproteolytic products of the fusion protein by determination of their N-terminal amino acid sequence. The 16-kDa protein arises from internal initiation. Following substitution of the 37 amino acids at the C-terminus of 3C, the autolytic activity was no longer observed. The recombinant proteinase did not show trans-activity when recombinant proteins of the P1 or P2 region were used as substrates. Antisera directed against recombinant 3C could not detect 3C or its precursors in HAV-infected cells.