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    Structural basis for translocation by AddAB helicase–nuclease and its arrest at χ sites

    Krajewski, Wojciech W. and Fu, X. and Wilkinson, M. and Cronin, N.B. and Dillingham, M.S. and Wigley, D.B. (2014) Structural basis for translocation by AddAB helicase–nuclease and its arrest at χ sites. Nature 508 , pp. 416-419. ISSN 0028-0836.

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    Abstract

    In bacterial cells, processing of double-stranded DNA breaks for repair by homologous recombination is dependent upon the recombination hotspot sequence χ (Chi)1, 2 and is catalysed by either an AddAB- or RecBCD-type helicase–nuclease (reviewed in refs 3, 4). These enzyme complexes unwind and digest the DNA duplex from the broken end until they encounter a χ sequence5, whereupon they produce a 3′ single-stranded DNA tail onto which they initiate loading of the RecA protein6. Consequently, regulation of the AddAB/RecBCD complex by χ is a key control point in DNA repair and other processes involving genetic recombination. Here we report crystal structures of Bacillus subtilis AddAB in complex with different χ-containing DNA substrates either with or without a non-hydrolysable ATP analogue. Comparison of these structures suggests a mechanism for DNA translocation and unwinding, suggests how the enzyme binds specifically to χ sequences, and explains how χ recognition leads to the arrest of AddAB (and RecBCD) translocation that is observed in single-molecule experiments7, 8, 9.

    Metadata

    Item Type: Article
    School: Birkbeck Schools and Departments > School of Science > Biological Sciences
    Depositing User: Administrator
    Date Deposited: 31 Mar 2014 09:27
    Last Modified: 02 Jun 2014 12:11
    URI: http://eprints.bbk.ac.uk/id/eprint/9477

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