title: Mycobacterium tuberculosis RecG binds and unwinds model DNA substrates with a preference for Holliday junctions.
abstract: The RecG enzyme, a superfamily 2 helicase, is present in nearly all bacteria. Here we report for the first time that the recG gene is also present in the genomes of most vascular plants as well as in green algae, but is not found in other eukaryotes or archaea. The precise function of RecG is poorly understood, although ample evidence shows that it plays critical roles in DNA repair, recombination and replication. We further demonstrate that Mycobacterium tuberculosis RecG (RecG(Mtb)) DNA binding activity had a broad substrate specificity, whereas it only unwound branched-DNA substrates such as Holliday junctions (HJs), replication forks, D-loops and R-loops, with a strong preference for the HJ as a helicase substrate. In addition, RecG(Mtb) preferentially bound relatively long (≥40 nt) ssDNA, exhibiting a higher affinity for the homopolymeric nucleotides poly(dT), poly(dG) and poly(dC) than for poly(dA). RecG(Mtb) helicase activity was supported by hydrolysis of ATP or dATP in the presence of Mg(2+), Mn(2+), Cu(2+) or Fe(2+). Like its Escherichia coli orthologue, RecG(Mtb) is also a strictly DNA-dependent ATPase.
authors.affiliation: Centre for Molecular Biology and Neuroscience and Department of Microbiology, University of Oslo, Oslo, Norway.
authors.forename: Ephrem Debebe
authors.initials: ED
authors.lastname: Zegeye
authors.affiliation: Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway.|Centre for Molecular Biology and Neuroscience and Department of Microbiology, University of Oslo, Oslo, Norway.
authors.forename: Seetha V
authors.initials: SV
authors.lastname: Balasingham
authors.affiliation: Bioinformatics Core Facility, Department of Informatics, University of Oslo, Oslo, Norway.|Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway.|Centre for Molecular Biology and Neuroscience and Department of Microbiology, University of Oslo, Oslo, Norway.
authors.forename: Jon K
authors.initials: JK
authors.lastname: Laerdahl
authors.affiliation: Centre for Molecular Biology and Neuroscience and Department of Microbiology, University of Oslo, Oslo, Norway.
authors.forename: Håvard
authors.initials: H
authors.lastname: Homberset
authors.affiliation: Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway.|Centre for Molecular Biology and Neuroscience and Department of Microbiology, University of Oslo, Oslo, Norway.
authors.forename: Tone
authors.initials: T
authors.lastname: Tønjum
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004265:DNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D045566:DNA, Cruciform / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D045566:DNA, Cruciform; D004265:DNA Helicases