title: Dda helicase unwinds a DNA-PNA chimeric substrate: evidence for an inchworm mechanism.
abstract: Helicases are ubiquitous enzymes involved in all aspects of DNA metabolism including replication, repair, recombination, and transcription. The mechanism of the bacteriophage T4 Dda helicase was investigated by preparing a DNA-PNA chimeric substrate. Surprisingly, Dda was able to unwind a substrate containing 12 PNA moieties in the loading strand of the enzyme. We suggest a mechanism whereby the Dda helicase contains two distinct DNA binding domains which allow an inchworm mechanism for translocation. A single step of the enzyme is sufficient to unwind the DNA-PNA chimera because several base pairs melt spontaneously due to thermal fraying. Hence, Dda helicase can unwind the substrate without actually translocating along the PNA.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
authors.forename: Travis L
authors.initials: TL
authors.lastname: Spurling
authors.forename: Robert L
authors.initials: RL
authors.lastname: Eoff
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Raney
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004265:DNA Helicases / Q000378:metabolism*; D020135:Peptide Nucleic Acids / Q000737:chemistry / Q000378:metabolism*
chemical_list: D020135:Peptide Nucleic Acids; D004247:DNA; D004265:DNA Helicases