title: Mechanism for nuclease regulation in RecBCD.
abstract: In bacterial cells, processing of double-stranded DNA breaks for repair by homologous recombination is catalysed by AddAB, AdnAB or RecBCD-type helicase-nucleases. These enzyme complexes are highly processive, duplex unwinding and degrading machines that require tight regulation. Here, we report the structure of E.coli RecBCD, determined by cryoEM at 3.8 Å resolution, with a DNA substrate that reveals how the nuclease activity of the complex is activated once unwinding progresses. Extension of the 5'-tail of the unwound duplex induces a large conformational change in the RecD subunit, that is transferred through the RecC subunit to activate the nuclease domain of the RecB subunit. The process involves a SH3 domain that binds to a region of the RecB subunit in a binding mode that is distinct from others observed previously in SH3 domains and, to our knowledge, this is the first example of peptide-binding of an SH3 domain in a bacterial system.
authors.affiliation: Section of Structural Biology, Department of Medicine, Imperial College London, London, United Kingdom.
authors.forename: Martin
authors.initials: M
authors.lastname: Wilkinson
authors.affiliation: Section of Structural Biology, Department of Medicine, Imperial College London, London, United Kingdom.
authors.forename: Yuriy
authors.initials: Y
authors.lastname: Chaban
authors.affiliation: Section of Structural Biology, Department of Medicine, Imperial College London, London, United Kingdom.
authors.forename: Dale B
authors.identifier: 0000-0002-0786-6726
authors.initials: DB
authors.lastname: Wigley
mesh_terms: D020285:Cryoelectron Microscopy; D004247:DNA / Q000737:chemistry* / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D043211:Exodeoxyribonuclease V / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D011487:Protein Conformation
chemical_list: D004247:DNA; D043211:Exodeoxyribonuclease V
keywords: DNA repair; E. coli; RecBCD; biophysics; chromosomes; genes; homologous recombination; structural biology