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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.
E H Poll, and
R M Benbow
October 1993,
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E H Poll, and
R M Benbow
December 1982,
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E H Poll, and
R M Benbow
March 1983,
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E H Poll, and
R M Benbow
January 1974,
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E H Poll, and
R M Benbow
May 1974,
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E H Poll, and
R M Benbow
March 1989,
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E H Poll, and
R M Benbow
April 1978,
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E H Poll, and
R M Benbow
July 1976,
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E H Poll, and
R M Benbow
January 1984,
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E H Poll, and
R M Benbow
December 1976,
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