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.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Adenosine Triphosphatases / chemistry
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Adenosine Triphosphatases / physiology*
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Adenosine Triphosphate / metabolism*
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DNA Breaks, Double-Stranded
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DNA Helicases / chemistry
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DNA Helicases / physiology*
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DNA Repair / physiology*
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DNA, Bacterial / metabolism
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Escherichia coli / enzymology
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Escherichia coli Proteins / chemistry
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Escherichia coli Proteins / physiology*
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Exodeoxyribonuclease V / chemistry
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Exodeoxyribonuclease V / physiology*
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Models, Molecular
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Molecular Motor Proteins / physiology
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Multienzyme Complexes
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Protein Binding
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Protein Conformation
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Protein Subunits
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / physiology
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Structure-Activity Relationship
Substances
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DNA, Bacterial
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Escherichia coli Proteins
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Molecular Motor Proteins
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Multienzyme Complexes
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Protein Subunits
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Recombinant Fusion Proteins
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Adenosine Triphosphate
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Exodeoxyribonuclease V
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exodeoxyribonuclease V, E coli
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Adenosine Triphosphatases
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DNA Helicases