The AddAB helicase–nuclease catalyses rapid and processive DNA unwinding using a single Superfamily 1A motor domain
Open Access
- 10 November 2010
- journal article
- research article
- Published by Oxford University Press (OUP) in Nucleic Acids Research
- Vol. 39 (6), 2271-2285
- https://doi.org/10.1093/nar/gkq1124
Abstract
The oligomeric state of Superfamily I DNA helicases is the subject of considerable and ongoing debate. While models based on crystal structures imply that a single helicase core domain is sufficient for DNA unwinding activity, biochemical data from several related enzymes suggest that a higher order oligomeric species is required. In this work we characterize the helicase activity of the AddAB helicase–nuclease, which is involved in the repair of double-stranded DNA breaks in Bacillus subtilis . We show that the enzyme is functional as a heterodimer of the AddA and AddB subunits, that it is a rapid and processive DNA helicase, and that it catalyses DNA unwinding using one single-stranded DNA motor of 3′→5′ polarity located in the AddA subunit. The AddB subunit contains a second putative ATP-binding pocket, but this does not contribute to the observed helicase activity and may instead be involved in the recognition of recombination hotspot sequences.Keywords
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