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A DNA helicase from Xenopus laevis ovaries
1Department of Zoology, Iowa State University, Ames 50011-3223.
Biochemistry
|November 29, 1988
Summary
Researchers purified a novel DNA helicase from Xenopus laevis ovaries. This enzyme unwinds DNA using ATP hydrolysis and differs from other known eukaryotic DNA helicases.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- DNA helicases are essential enzymes involved in DNA replication, repair, and recombination.
- Understanding the diversity of DNA helicases is crucial for comprehending various DNA metabolic processes.
Purpose of the Study:
- To extensively purify and characterize a DNA helicase from Xenopus laevis ovaries.
- To determine the biochemical properties and potential novelty of this enzyme.
Main Methods:
- Extensive purification of DNA helicase from Xenopus laevis ovaries.
- Biochemical assays to assess enzyme activity, cofactor requirements, and molecular weight.
- Analysis of enzyme properties including Stokes radius and sedimentation coefficient.
Main Results:
- A highly purified DNA helicase fraction was obtained, free from contaminating enzymatic activities.
- The enzyme's native molecular weight was calculated to be 140,000-170,000.
- DNA helicase activity required divalent cations (Mg2+ or Mn2+) and ATP/dATP hydrolysis, with optimal stimulation by monovalent cations (K+, Na+).
- DNA-dependent ATPase activity copurified with the helicase, with single-stranded DNA being a more efficient cofactor.
Conclusions:
- The purified Xenopus laevis DNA helicase exhibits unique biochemical properties.
- Its distinct characteristics, including molecular weight and cofactor dependencies, suggest it is a novel type of eukaryotic DNA helicase.