HCV-NS5-G1 protein.The protein contains the HCV-NS5 genotype 1 immunodominant regions.Hepatitis C Virus NS5 protein is purified by proprietarychromatographic techniques.The hepatitis C virus (HCV) NS5A gene product is aphosphorylated 56-to 58-kD nonstructural protein thatdisplays a multitude of activities related to enhancementof viral pathogenesis. Although associated with otherviral encoded proteins as part of the viral replicasecomplex positioned on the cytoplasmic side of the endoplasmic reticulum, a role for NS5A in viral replicationhas not been defined. Truncated versions of NS5A canact as transcriptional activators, while other recentlycharacterized interactions of NS5A with cellular proteinsindicate its pleiotropic role in HCV-host interactions.It has been shown that NS5B is a membraneassociatedprotein, which contains a C-terminal domain comprising21 hydrophobic amino acids that is responsible formembrane anchorage. NS5B may form a complex withcellular proteins or other HCV nonstructural proteins,including NS3, the viral protease and helicase; NS4A,a cofactor of NS3 protease activity; and NS5A,a phosphoprotein containing a putative interferon sensitivity region. Although the HCV replication mechanismis not clearly understood, the essential role of NS5Bpolymerase in the HCV replication and infection processhas been demonstrated in chimpanzees. Accordingly,it has been viewed as an attractive target for antiviralintervention. Purity >95% by SDS-PAGE and RP-HPLC