title: Purification and characterization of a DNA helicase from pea chloroplast that translocates in the 3'-to-5' direction.
abstract: An ATP-dependent DNA helicase has been purified to near homogeneity from pea chloroplasts. The enzyme is a homodimer of 68-kDa subunits. The purified enzyme shows DNA-dependent ATPase activity and is devoid of DNA polymerase, DNA topoisomerase, DNA ligase or nuclease activities. The enzyme requires Mg2+ or Mn2+ for its maximum activity. ATP is the most favoured cofactor for this enzyme while other NTP or dNTP are poorly utilized. Pea chloroplast DNA helicase can unwind a 17-bp duplex whether it has unpaired single-stranded tails at both the 5' end and 3' end, at the 5' end or at the 3' end only, or at neither end. However, it fails to act on a blunt-ended 17-bp duplex DNA. The enzyme moves unidirectionally from 3' to 5' along the bound strand. The unwinding activity is inhibited by the intercalating drugs nogalamycin and daunorubicine.
authors.affiliation: International Centre for Genetic Engineering and Biotechnology, New Delhi, India.
authors.forename: N
authors.initials: N
authors.lastname: Tuteja
authors.forename: T N
authors.initials: TN
authors.lastname: Phan
authors.forename: K K
authors.initials: KK
authors.lastname: Tewari
mesh_terms: D001483:Base Sequence; D001667:Binding, Competitive; D002412:Cations / Q000378:metabolism; D002482:Cellulose / Q000737:chemistry; D002736:Chloroplasts / Q000737:chemistry / Q000201:enzymology; D002853:Chromatography, Liquid / Q000379:methods; D004247:DNA / Q000737:chemistry; D004265:DNA Helicases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000737:chemistry; D006493:Heparin / Q000737:chemistry; D006657:Histones / Q000494:pharmacology; D008956:Models, Chemical; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009621:Nogalamycin / Q000494:pharmacology; D018532:Pisum sativum / Q000737:chemistry* / Q000201:enzymology*; D012685:Sepharose / Q000737:chemistry; D013379:Substrate Specificity
chemical_list: D002412:Cations; D004277:DNA, Single-Stranded; D006657:Histones; D002482:Cellulose; D006493:Heparin; D004247:DNA; D012685:Sepharose; D004265:DNA Helicases; D009621:Nogalamycin