NS2

The nonstructural protein 2 (NS2) has dual functions in the HCV life cycle—as a cysteine protease and as a cofactor in the assembly process. The protease domain of the NS2 protein, in cooperation with the N-terminal region of NS3, functions as a cysteine protease to catalyze a single cleavage between the NS2 and NS3 proteins. The freeing of the NS2 from NS3 is essential for RNA replication. The NS2 protein is not required for HCV RNA replication, but in conjunction with multiple other viral proteins, it plays a key role in coordinating viral assembly. Specifically, it appears that during viral assembly, NS2 colocalizes with E1, E2, NS3, and NS5A near the core proteins and lipid droplet.