Insights into resistance mechanism of hepatitis C virus nonstructural 3/4A protease mutant to boceprevir using umbrella sampling simulation study.

Hepatitis C virus can cause inflammation in human liver cells, leading to liver cirrhosis and liver cancer. Based on the World Health Organization reports, about 228 million people in the world have hepatitis C. To date, some inhibitory medicines against the hepatitis C virus nonstructural 3/4A protease, such as boceprevir, have entered clinical trial phases. However, several hepatitis C virus nonstructural 3/4A protease mutations have been recognized to decrease susceptibility of boceprevir to hepatitis C virus. The molecular details behind inhibitor resistance of these single-point mutations are not still understood. Thus, in this research, computational strategies were applied to clarify the inhibitor resistance mechanism. From umbrella sampling simulation and energy profiles, the polar interactions are the main driving force for boceprevir binding. Based on the analyzed R155T mutant, the main reason for the occurrence of boceprevir resistance is the conformation alterations of S4 and extended S2 binding pockets. These changes, lead to decreased binding ability of the key residues to P2 and P4 moieties of boceprevir. Moreover, structural results show that the disappearance of important salt bridges can bring about the great conformation changes of the binding pockets in R155T.Communicated by Ramaswamy H. Sarma.