New Direct Acting Anti-Virals Inhibiting Hepatitis C Virus Helicase and Insights into How ATP Fuels Helicase Action

Abstract

According to the World Health Organization, Hepatitis C Virus (HCV) has infected 130-150 million people worldwide. Approximately 700,000 of those die each year from chronic HCV related causes such as cirrhosis or cancer. Currently, there are numerous HCV drugs on the market; they target the protease, polymerase and NS5A proteins encoded by of HCV. These drugs are expensive and HCV can become resistant, thus there is constant need for new DAAs. The first part of this thesis examines the search for additional drugs that function by inhibiting the NS3 helicase, which have been challenging to develop. Part of the reason for a lack of helicase inhibitors can be due to the difficulty of understanding its mechanism. The helicase is a motor protein that couples ATP hydrolysis to DNA or RNA unwinding. The second part of this thesis examine the role of a cysteine residue in the helicase ATP binding site. When the cysteine was replaced with other amino acids, the protein possessed unusual features not seen in the wildtype helicase. Helicase proteins lacking the cysteine, were able to hydrolyze ATP in the absence of nucleic acid 15times faster than wildtype. This finding may provide future information into the coupling mechanism of chemical energy to physical motions of the enzyme.