Inhibition of the hepatitis C virus NS3/4A protease - The crystal structures of two protease-inhibitor complexes

The hepatitis C virus NS3 protein contains a serine protease domain with a chymotrypsin-like fold, which is a target for development of therapeutics. We report the crystal structures of this domain complexed with NS4A cofacto r and with two potent, reversible covalent inhibitors spanning the P1-P4 re sidues. Both inhibitors bind in an extended backbone conformation, forming an antiparallel beta-sheet with one enzyme beta-strand. The P1 residue cont ributes most to the binding energy, whereas P2-P4 side chains are partially solvent exposed. The structures do not show notable rearrangements of the active site upon inhibitor binding. These results are significant for the d evelopment of antivirals.