DNA helicase

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DNA helicase[1] is an enzyme responsible for the separation of two annealed strands of nucleic acids. It binds to the double stranded DNA, and breaks the hydrogen bonds between the strands. This process allows a single-stranded DNA to form and be used as a template during transcription. ATP hydrolysis provides the energy for the enzyme to translocate along the double helix and generate a replication fork[2].

In E. coli DNA helicase is called the DnaB protein, and it differs slightly in the way it carries out it's function. DnaB forms a three-fold ring structure, with the lagging strand binding in the central region, whilst the leading strand is excluded. The DnaB translocates through a mechanism where dNTP's bind and cause a conformational change, forcing the DNA strands to separate[3].

Approximately 1% of eukaryotic genes code for helicases. The human genome codes for 95 non-redundant helicases: 64 RNA helicases and 31 DNA helicases.

References

  1. Kitao, Saori et. al. 1998. Cloning of Two New Human Helicase Genes of the RecQ Family: Biological Significance of Multiple Species in Higher Eukaryotes. Genomics 54: 443-452.
  2. Alberts, Johnson, Lewis, Raff, Roberts, Walters. (2008) Molecular Biology of the Cell: 273, 5th edition, New York: Garland Science.
  3. Alberts, Johnson, Lewis, Raff, Roberts, Walters. (2008) Molecular Biology of the Cell: 283, 5th edition, New York: Garland Science.
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