A DNA helicase from Xenopus laevis ovaries

• Published in: Biochemistry (Easton) Vol. 27; no. 24; pp. 8701 - 8706
• Main Authors: Poll, E. H. A, Benbow, Robert M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.11.1988
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Cations, Divalent; Chromatography; Chromatography, Affinity; Chromatography, Ion Exchange; DNA Topoisomerases, Type I - isolation & purification; DNA Topoisomerases, Type I - metabolism; Durapatite; Enzymes and enzyme inhibitors; Female; Fundamental and applied biological sciences. Psychology; Hydroxyapatites; Isomerases; Kinetics; Molecular Weight; Ovary - enzymology; Protein Conformation; Ultracentrifugation; Xenopus laevis; Ovary; Vertebrata; Purification; Enzymatic activity; DNA; Xenopus laevis; Amphibia; Salientia; Column chromatography; Cofactor; Unwinding enzyme
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00424a002

A DNA helicase was extensively purified from Xenopus laevis ovaries. The most purified fraction was free of DNA topoisomerase, DNA polymerase, and nuclease activities. The enzyme had a Stokes radius of 54 A and a sedimentation coefficient of 6-7.3 S, from which a native molecular weight of 140,000-170,000 was calculated. DNA helicase activity required Mg2+ or Mn2+ and was dependent on hydrolysis of ATP or dATP. Monovalent cations, K+ and Na+, stimulated DNA unwinding with an optimum at 130 mM. DNA-dependent ATPase activity copurified with the X. laevis DNA helicase. Double-stranded and single-stranded DNA were both cofactors for the ATPase activity, but single-stranded DNA was more efficient. The molecular weight, monovalent cation dependence, cofactor requirements, and elution from single-stranded DNA-cellulose suggest that the X. laevis DNA helicase is different from previously described eukaryotic DNA helicases.