Enzymatic characterization of purified NS3 serine proteinase of hepatitis C virus expressed in Escherichia coli

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Abstract
Non‐structural protein 3 (NS3) of the hepatitis C virus (HCV) has been shown to be a serine proteinase which cleaves the HCV polyprotein thus activating its replicative machinery. To characterize enzymatic activities of NS3 serine proteinase, the proteinase region was expressed in Escherichia coli and purified. The purified proteinase specifically cleaved a purified fusion protein sandwiching the NS5A/5B cleavage sequence. In addition to serine proteinase inhibitors, some chelators also inhibited the cleavage activity. Metal ions were not required for its activity, suggesting that the proteinase may be a novel serine proteinase having a unique binding site for chelators.