DNA-Protein Interactions Unit, School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, UK.
Nucleic Acids Res. 2011 Mar;39(6):2271-85. doi: 10.1093/nar/gkq1124. Epub 2010 Nov 10.
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.
I 型 DNA 解旋酶的寡聚状态是一个备受关注且仍在讨论中的话题。虽然基于晶体结构的模型表明，单个解旋酶核心结构域足以进行 DNA 解旋活性，但来自几种相关酶的生化数据表明，需要更高阶的寡聚物种。在这项工作中，我们对枯草芽孢杆菌双链 DNA 断裂修复中涉及的 AddAB 解旋酶-核酸酶的解旋酶活性进行了表征。我们表明，该酶作为 AddA 和 AddB 亚基的异二聚体发挥功能，它是一种快速和连续的 DNA 解旋酶，并且使用位于 AddA 亚基中的单个 3' → 5' 极性单链 DNA 马达催化 DNA 解旋。AddB 亚基包含第二个假定的 ATP 结合口袋，但这对观察到的解旋酶活性没有贡献，而可能参与重组热点序列的识别。
