title: The Escherichia coli RecQ helicase functions as a monomer.
abstract: The RecQ helicases belong to an important family of highly conserved DNA helicases that play a key role in chromosomal maintenance, and their defects have been shown to lead to several disorders and cancer in humans. In this work, the conformational and functional properties of the Escherichia coli RecQ helicase have been determined using a wide array of biochemical and biophysical techniques. The results obtained clearly indicate that E. coli RecQ helicase is monomeric in solution up to a concentration of 20 microM and in a temperature range between 4 and 37 degrees C. Furthermore, these properties are not affected by the presence of ATP, which is strictly required for the unwinding and translocating activity of the protein, or by its nonhydrolyzable analogue 5'-adenylyl-beta,gamma-imidodiphosphate. Consistent with the structural properties, functional analysis shows that both DNA unwinding activity and single-stranded DNA-stimulated ATPase specific activity were independent of RecQ concentration. The monomeric state was further confirmed by the ATPase-deficient mutants of RecQ protein. The rate of unwinding was unchanged when the wild type RecQ helicase was mixed with the ATPase-deficient mutants, indicating that nonprotein-protein interactions were involved in the unwinding processes. Taken together, these results indicate that RecQ helicase functions as a monomer and provide new data on the structural and functional properties of RecQ helicase that may help elucidate its mechanism action.
authors.affiliation: Laboratoire de Biotechnologies et Pharmacologie Génétique Appliquée CNRS UMR 8113, Ecole Normale Supérieure de Cachan, 61 Avenue du Président Wilson, 94235 Cachan cedex, France.
authors.forename: Hou Qiang
authors.initials: HQ
authors.lastname: Xu
authors.forename: Eric
authors.initials: E
authors.lastname: Deprez
authors.forename: Ai Hua
authors.initials: AH
authors.lastname: Zhang
authors.forename: Patrick
authors.initials: P
authors.lastname: Tauc
authors.forename: Moncef M
authors.initials: MM
authors.lastname: Ladjimi
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Brochon
authors.forename: Christian
authors.initials: C
authors.lastname: Auclair
authors.forename: Xu Guang
authors.initials: XG
authors.lastname: Xi
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019943:Amino Acid Substitution; D001483:Base Sequence; D001665:Binding Sites; D004265:DNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D053484:RecQ Helicases; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015183:Restriction Mapping; D012996:Solutions
chemical_list: D004269:DNA, Bacterial; D011994:Recombinant Proteins; D012996:Solutions; D000251:Adenosine Triphosphatases; C506724:RecQ protein, E coli; D004265:DNA Helicases; D053484:RecQ Helicases