Hepatitis G Virus Encodes Protease Activities Which Can Effect Processing of the Virus Putative Nonstructural Proteins

The genome of a recently identified virus, hepatitis G virus (HGV), shows considerable homology to hepatitis C virus (HCV). Two HGV proteases similar to nonstructural proteins NS2 and NS3 of HCV were identified, and their cleavage site specificity was investigated. Amino acids essential for the protease activities were determined by mutation analysis. NS4A of HGV was demonstrated to be a cofactor for NS3-mediated proteolysis, with a region critical for activity residing between Leu(1561) and Ala(1598).