title: Single-molecule imaging of Bacteroides fragilis AddAB reveals the highly processive translocation of a single motor helicase.
abstract: The AddAB helicase and nuclease complex is used for repairing double-strand DNA breaks in the many bacteria that do not possess RecBCD. Here, we show that AddAB, from the Gram-negative opportunistic pathogen Bacteroides fragilis, can rescue the ultraviolet sensitivity of an Escherichia coli recBCD mutant and that addAB is required for survival of B. fragilis following DNA damage. Using single-molecule observations we demonstrate that AddAB can translocate along DNA at up to 250 bp per second and can unwind an average of 14,000 bp, with some complexes capable of unwinding 40,000 bp. These results demonstrate the importance of processivity for facilitating encounters with recognition sequences that modify enzyme function during homologous recombination.
authors.affiliation: EastChem School of Chemistry and COSMIC, The University of Edinburgh, The King's Buildings, Edinburgh EH9 3JR, UK.
authors.forename: Marcel
authors.initials: M
authors.lastname: Reuter
authors.forename: Frances
authors.initials: F
authors.lastname: Parry
authors.forename: David T F
authors.initials: DT
authors.lastname: Dryden
authors.forename: Garry W
authors.initials: GW
authors.lastname: Blakely
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001441:Bacteroides fragilis / Q000201:enzymology* / Q000235:genetics; D004249:DNA Damage; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000528:radiation effects; D005090:Exodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D021381:Protein Transport; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; D005090:Exodeoxyribonucleases; C407424:AddAB enzyme; D004265:DNA Helicases