Helicase is an enzyme vital to all living organisms. Its function is to temporarily separate the two strands of a DNA double helix so that DNA or RNA synthesis can take place. RNA polymerase has its own helicase activity, whereas in DNA polymerase the helicase is a separate subunit.
Helicase subunit in DNA polymerase is a donut-shaped enzyme and is produced by the DnaBgene. In conjunction with DNA primase helicase promotes DNA unwinding by binding to the initiator proteins and loading into the DNA. Helicase then denatures (untwists) the DNA by hydrolysis of adenosine triphosphate (ATP). Continuous hydrolysis of ATP allows helicase to move along the single strand of DNA, untwisting doube-stranded DNA that it encounters. An enzyme topoisomerase binds to the double-stranded DNA downstream of the unwound DNA to prevent excess strain on the helix.
DNAHelicase and Exonuclease Activities Are Encoded by Distinct Domains of the WRN Gene-- An N-terminal domain in WRN was recently shown to encode a DNA sequence motif that is conserved in several exonucleases (28-30).
Glycerol gradient centrifugation of WRN DNAhelicase and exonuclease.
DNAhelicase, WRN protein was incubated for 1 h at 4 °C with the indicated amounts of preimmune serum (A) or anti-WRN antiserum (B).
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