Key binding and susceptibility of NS3/4A serine protease inhibitors against hepatitis C virus

Hepatitis C virus (HCV) causes an infectious disease that manifests itself as liver inflammation, cirrhosis, and can lead to the development of liver cancer. Its NS3/4A serine protease is a potent target for drug design and development since it is responsible for cleavage of the scissile peptide bonds in the polyprotein important for the HCV life cycle. Herein, the ligand-target interactions and the binding free energy of the four current NS3/4A inhibitors (boceprevir, telaprevir, danoprevir, and BI201335) were investigated by all-atom molecular dynamics simulations with three different initial atomic velocities. The per-residue free energy decomposition suggests that the key residues involved in inhibitor binding were residues 41-43, 57, 81, 136-139, 155-159, and 168 in the NS3 domain. The van der Waals interactions yielded the main driving force for inhibitor binding at the protease active site for the cleavage reaction. In addition, the highest number of hydrogen bonds was formed at the reactive P1 site of the four studied inhibitors. Although the hydrogen bond patterns of these inhibitors were different, their P3 site was most likely to be recognized by the A157 backbone. Both molecular mechanic (MM)/Poisson-Boltzmann surface area and MM/generalized Born surface area approaches predicted the relative binding affinities of the four inhibitors in a somewhat similar trend to their experimentally derived biological activities.