Virus-encoded enzymes of hepatitis C virus (HCV) were identified from
its genome sequence. This allows application of drug discovery strateg
ies which rely on inhibition of enzymes unique to HCV. Discovery of hi
gh-affinity inhibitors is facilitated by knowledge of the target enzym
e's three-dimensional structure. For development of inhibitors of the
HCV helicase, which belongs to a class of enzymes for which little str
uctural information is available, the impact of structural information
on the drug discovery process is greater than for targets belonging t
o well-characterized classes of enzyme. Here the structure of the HCV
helicase is described. Regions required for enzymatic activity, which
are also the preferred sites of drug interaction, are highlighted.