1. Biochemistry and Chemical Biology
  2. Structural Biology and Molecular Biophysics
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Mechanochemical coupling and bi-phasic force-velocity dependence in the ultra-fast ring ATPase SpoIIIE

  1. Ninning Liu
  2. Gheorghe Chistol
  3. Yuanbo Cui
  4. Carlos Bustamante  Is a corresponding author
  1. University of California, Berkeley, United States
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Cite this article as: eLife 2018;7:e32354 doi: 10.7554/eLife.32354

Abstract

Multi-subunit ring-shaped ATPases are molecular motors that harness chemical free energy to perform vital mechanical tasks such as polypeptide translocation, DNA unwinding, and chromosome segregation. Previously we reported the intersubunit coordination and stepping behavior of the hexameric ring-shaped ATPase SpoIIIE (Liu et al., 2015). Here we use optical tweezers to characterize the motor's mechanochemistry. Analysis of the motor response to external force at various nucleotide concentrations identifies phosphate release as the likely force-generating step. Analysis of SpoIIIE pausing indicates that pauses are off-pathway events. Characterization of SpoIIIE slipping behavior reveals that individual motor subunits engage DNA upon ATP binding. Furthermore, we find that SpoIIIE's velocity exhibits an intriguing bi-phasic dependence on force. We hypothesize that this behavior is an adaptation of ultra-fast motors tasked with translocating DNA from which they must also remove DNA-bound protein roadblocks. Based on these results, we formulate a comprehensive mechanochemical model for SpoIIIE.

Article and author information

Author details

  1. Ninning Liu

    Jason L Choy Laboratory of Single Molecule Biophysics, University of California, Berkeley, Berkeley, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Gheorghe Chistol

    Jason L Choy Laboratory of Single Molecule Biophysics, University of California, Berkeley, Berkeley, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Yuanbo Cui

    Jason L Choy Laboratory of Single Molecule Biophysics, University of California, Berkeley, Berkeley, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Carlos Bustamante

    Jason L Choy Laboratory of Single Molecule Biophysics, University of California, Berkeley, Berkeley, United States
    For correspondence
    carlosb@berkeley.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-2970-0073

Funding

Howard Hughes Medical Institute

  • Carlos Bustamante

National Institutes of Health (R01GM071552)

  • Carlos Bustamante

National Institutes of Health (R01GM032543)

  • Carlos Bustamante

U.S. Department of Energy (DE-AC02-05CH11231)

  • Carlos Bustamante

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Taekjip Ha, Johns Hopkins University School of Medicine, United States

Publication history

  1. Received: September 28, 2017
  2. Accepted: March 3, 2018
  3. Accepted Manuscript published: March 5, 2018 (version 1)
  4. Version of Record published: March 19, 2018 (version 2)

Copyright

© 2018, Liu et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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