ANALYSIS OF N-TERMINAL PROCESSING OF HEPATITIS-C VIRUS NONSTRUCTURAL PROTEIN-2

We determined the partial amino (N)-terminal amino acid sequence of hepatitis C virus p21(nonstructural protein 2 [NS2]). Cleavage at the p21 (NS2) N terminus depended on the presence of microsomal membranes. The amino-terminal position of p21(NS2) was assigned to amino acid 810 of the hepatitis C virus strain IIj precursor polyprotein. Mutation of the alanine residue at position P1 of the putative cleavage site inhibited membrane-dependent processing. This alteration in processing together with the fact that hydrophobic amino acid residues are clustered upstream of the putative cleavage site suggested the involvement of a signal peptidase(s) in the cleavage. Furthermore, mutation analysis of this possible cleavage site revealed the presence of another microsome membrane-dependent cleavage site upstream of the N terminus of p21 (NS2).