Inhibitor-resistant HCV NS3 protease
An inhibitor-resistant HCV NS3 protease is provided which is useful to screen for compounds having therapeutic value against drug resistant HCV strains. In particular, the inhibitor-resistant HCV NS3 protease comprises an amino acid sequence which is mutated in the substrate binding pocket thereof rendering the protease resistant to inhibitor. In a specific aspect of the present invention, at least one of the amino acids at position 155, 156 and 168 of the HCV NS3 protease is mutated to yield an inhibitor-resistant protease.
1. An isolated, variant, inhibitor-resistant, HCV NS3 protease having serine protease activity comprising an HCV NS3 protease amino acid sequence wherein said variant comprises a substitution of the amino acid at the position corresponding to position 156 of SEQ ID NO:2 with a non-alanine amino acid.
2. The variant protease according to claim 1 , wherein said amino acid sequence set forth in SEQ ID NO:2, comprises an amino acid substitution selected from the group consisting of A156G, A156T, and A156V.
3. The variant protease according to claim 1 or 2 , further comprising one or more amino acid substitutions selected from the group consisting of S20N, R26K, Q28R, A39T, Q41R, I71V, Q80R, Q86R, P89L, P89S, S101N, A111S, P115S, S122R, R155Q, L144F, A150V, R155W, V158L, D168A, D168G, D168H, D168N, D168V, E176K, T178S, M179I, M179V, and M179T.
4. An isolated, variant, inhibitor-resistant, HCV NS3 protease comprising an amino acid sequence which is at least 90% identical to the amino acid sequence of SEQ ID NO:2, wherein said variant comprises an amino acid substitution at the position corresponding to position 156 of SEQ ID NO:2 selected from the group consisting of A156G, A156T, and A156V.
5. The variant protease according to claim 4 , further comprising one or more amino acid substitutions selected from the group consisting of S20N, R26K, Q28R, A39T, Q41R, I71V, Q80R, Q86R, P89L, P89S, S101N, A111S, P115S, S122R, R155Q, L144F, A150V, R155W, V158L, D168A, D168G, D168H, D168N, D168V, E176K, T178S, M179I, M179V, and M179T.
6. A method for identifying inhibitor of HCV NS3 protease activity comprising:
incubating an inhibitor-resistant NS3 protease variant as defined in claim 1 in the presence or absence of a candidate inhibitor compound; and
measuring the protease activity of said inhibitor-resistant NS3 protease in the presence and absence of said candidate inhibitor compound;
wherein a decrease in activity of said protease in the presence of a candidate inhibitor indicates that said compound inhibits said HCV NS3 protease.