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Helicases |
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Helicases use energy generated by the hydrolysis
of nucleoside triphosphates (for example ATP) to break the hydrogen
bonds holding the strands together in duplex DNA and RNA. Helicases
are involved in every aspect of nucleic acid metabolism in the cell,
including DNA replication, repair, recombination, transcription,
and protein translation. Helicases can be grouped into two classes
based on the mechanism of unwinding: those that translocate in a
5’ to 3’ direction and those that travel in the opposite
3’ to 5’ direction. The 5’ to 3’ helicases
usually form hexameric ring structure and are mainly involved in
DNA replication. |
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| The UvrD helicase used in HDA reactions
is from the class of the 3’ to 5’ translocators. These
proteins exist as monomers or dimers and, unlike many other helicases,
UvrD helicase is able to melt fully duplex molecules (DNA fragment
with blunt ends) and nicked circular DNA molecules. UvrD is involved
in the two major DNA repair pathways: methyl-directed mismatch repair
and UvrABC-mediated nucleotide excision repair. In the methyl-directed
mismatch DNA repair pathway, UvrD is recruited to unwind the DNA strand
containing the DNA biosynthetic error. |
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Crystal structure pictures are obtained from Dr.
Dale Wigley, Cancer Research UK.
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