PMID:21071401

Citation	Yeeles, JT, Gwynn, EJ, Webb, MR and Dillingham, MS (2011) The AddAB helicase-nuclease catalyses rapid and processive DNA unwinding using a single Superfamily 1A motor domain. Nucleic Acids Res. 39:2271-85
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.
Links	PubMed PMC3064778 Online version:10.1093/nar/gkq1124
Keywords	Amino Acid Motifs; Biocatalysis; DNA/metabolism; DNA Helicases/chemistry; DNA Helicases/genetics; DNA Helicases/metabolism; DNA, Single-Stranded/metabolism; Dimerization; Exodeoxyribonucleases/chemistry; Exodeoxyribonucleases/genetics; Exodeoxyribonucleases/metabolism; Mutation; Protein Structure, Tertiary; Protein Subunits/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
LACF3:ADDA		GO:0006302: double-strand break repair	ECO:0000314:		P		Figure 5. A single helicase motor catalyses processive DNA unwinding by AddAB.	complete

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