COMPARISONS BETWEEN THE STRUCTURES OF HCV AND REP HELICASES REVEAL STRUCTURAL SIMILARITIES BETWEEN SF1 AND SF2 SUPER-FAMILIES OF HELICASES

Three helicase structures have been determined recently: that of the D NA helicase PcrA, that of the hepatitis C virus RNA helicase, and that of the Escherichia coli DNA helicase Rep. PcrA and Rep belong to the same super-family of helicases (SF1) and are structurally very similar . In contrast, the HCV helicase belongs to a different super-family of helicases, SF2, and shows little sequence homology with the PcrA/Rep helicases. Yet, the HCV helicase is structurally similar to Rep/PcrA, suggesting preservation of structural scaffolds and relationships betw een helicase motifs across these two super-families. The comparison st udy presented here also reveals the existence of a new helicase motif in the SF1 family of helicases.