3 years ago

Dynamics of DNA unwinding by helicases with frequent backward steps

XPD (Xeroderma pigmentosum complementation group D) is a prototypical 5′ – 3′ translocating DNA helicase that exhibits frequent backward steps during DNA unwinding. Here, we propose a model of DNA unwinding by XPD. With the model we explain why XPD exhibits frequent backsteps while other helicases show rare backsteps. We explain quantitatively the single-molecule data on probability of –1-bp step and mean dwell time of one step versus ATP concentration for XPD at fixed large external force applied to the ends of the DNA hairpin to unzip the hairpin. We study DNA unwinding velocity, probability of –1-bp step and mean dwell time of one step for XPD versus external force at various ATP concentrations. We compare DNA unwinding dynamics of the 5′ – 3′ helicase XPD with that of 3′ – 5′ helicase RecQ. Our results show that the DNA unwinding velocity of XPD is sensitively dependent on the external force, which is contrast to RecQ that shows insensitive dependence of DNA unwinding velocity on the external force, explaining the experimental data showing that RecQ is an “optimally active” helicase while XPD is a “partially active” helicase. The DNA unwinding dynamics of different helicases under the external force is also studied.

Publisher URL: www.sciencedirect.com/science

DOI: S0025556417305461

You might also like
Never Miss Important Research

Researcher is an app designed by academics, for academics. Create a personalised feed in two minutes.
Choose from over 15,000 academics journals covering ten research areas then let Researcher deliver you papers tailored to your interests each day.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.