Modulation of hepatitis C virus NS3 protease and helicase activities through the interaction with NS4A.

摘要: The hepatitis C virus nonstructural 3 protein (NS3) possesses a serine protease activity in the N-terminal one-third, whereas RNA-stimulated NTPase and helicase activities reside C-terminal portion. is required for proteolytic processing at NS3-NS4A, NS4A-NS4B, NS4B-NS5A, NS5A-NS5B polyprotein cleavage sites. NS3 forms complex with NS4A, 54-residue polypeptide that was shown to act as an essential cofactor of protease. We have expressed Escherichia coli NS3-NS4A precursor; junction between NS4A occurs during expression bacteria cells, resulting formation soluble noncovalent sub-nanomolar dissociation constant. assessed minimal ionic strength detergent glycerol concentrations maximal stability purified complex. Using peptide substrate derived from junction, catalytic efficiency (kcat/Km) NS3-NS4A-associated under optimized conditions 55 000 s-1 M-1, very similar measured recombinant eukaryotic cells. Dissociation found be fully reversible. No exhibited by complex, but active upon NS4A. On other hand, both basal poly(U)-induced ssRNA binding associated were those alone. Therefore, appears uncouple ATPase/ssRNA RNA unwinding NS3.