title: Escherichia coli RecBC helicase has two translocase activities controlled by a single ATPase motor.
abstract: E. coli RecBCD is a DNA helicase with two ATPase motors (RecB, a 3'→5' translocase, and RecD, a 5'→3' translocase) that function in repair of double-stranded DNA breaks. The RecBC heterodimer, with only the RecB motor, remains a processive helicase. Here we examined RecBC translocation along single-stranded DNA (ssDNA). Notably, we found RecBC to have two translocase activities: the primary translocase moves 3'→5', whereas the secondary translocase moves RecBC along the opposite strand of a forked DNA at a similar rate. The secondary translocase is insensitive to the ssDNA backbone polarity, and we propose that it may fuel RecBCD translocation along double-stranded DNA ahead of the unwinding fork and ensure that the unwound single strands move through RecBCD at the same rate after interaction with a crossover hot-spot indicator (Chi) sequence.
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Saint Louis, Missouri, USA.
authors.forename: Colin G
authors.initials: CG
authors.lastname: Wu
authors.forename: Christina
authors.initials: C
authors.lastname: Bradford
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Lohman
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded; D004265:DNA Helicases / Q000737:chemistry / Q000502:physiology*; D004260:DNA Repair / Q000502:physiology*; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000502:physiology*; D043211:Exodeoxyribonuclease V / Q000737:chemistry / Q000502:physiology*; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000502:physiology; D009097:Multienzyme Complexes; D011485:Protein Binding; D011487:Protein Conformation; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000502:physiology; D013329:Structure-Activity Relationship
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D020409:Molecular Motor Proteins; D009097:Multienzyme Complexes; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D000255:Adenosine Triphosphate; D043211:Exodeoxyribonuclease V; C468322:exodeoxyribonuclease V, E coli; D000251:Adenosine Triphosphatases; D004265:DNA Helicases