Testing the steric exclusion model for hexameric helicases: Substrate features that alter RNA-DNA unwinding by the transcription termination factor Rho

The potential relationship between helicase structural organization and unwinding mechanism is examined by performing in vitro Rho helicase experiments with model substrates containing an RNA-DNA helix downstream from a Rho loading site. The results have outlined the differences as well as the similarities in the mechanism of unwinding between Rho and other hexameric helicases, which are discussed in relation with the biological function of the Rho helicase.