Dda helicase tightly couples translocation on single-stranded DNA to unwinding of duplex DNA: Dda is an optimally active helicase.

ABSTRACT: Helicases utilize the energy of ATP hydrolysis to unwind double-stranded DNA while translocating on the DNA. Mechanisms for melting the duplex have been characterized as active or passive, depending on whether the enzyme actively separates the base pairs or simply sequesters single-stranded DNA (ssDNA) that forms due to thermal fraying. Here, we show that Dda translocates unidirectionally on ssDNA at the same rate at which it unwinds double-stranded DNA in both ensemble and single-molecule experiments. Further, the unwinding rate is largely insensitive to the duplex stability and to the applied force. Thus, Dda transduces all of its translocase activity into DNA unwinding activity so that the rate of unwinding is limited by the rate of translocation and that the enzyme actively separates t

SUBMITTER: Byrd AK 

PROVIDER: S-EPMC3372602 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature