1. Biochemistry and Chemical Biology
  2. Structural Biology and Molecular Biophysics

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
https://doi.org/10.7554/eLife.32354
Share this article
Cite this article
  1. Ninning Liu
  2. Gheorghe Chistol
  3. Yuanbo Cui
  4. Carlos Bustamante
(2018)
Mechanochemical coupling and bi-phasic force-velocity dependence in the ultra-fast ring ATPase SpoIIIE
eLife 7:e32354.
https://doi.org/10.7554/eLife.32354
  2. Download BibTeX
  3. Download .RIS

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.

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.

Metrics

  • 9
    citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.

Citations by DOI

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Ninning Liu
  2. Gheorghe Chistol
  3. Yuanbo Cui
  4. Carlos Bustamante
(2018)
Mechanochemical coupling and bi-phasic force-velocity dependence in the ultra-fast ring ATPase SpoIIIE
eLife 7:e32354.
https://doi.org/10.7554/eLife.32354

Share this article

https://doi.org/10.7554/eLife.32354

Categories and tags

Research organism

Further reading

    1. Structural Biology and Molecular Biophysics

    Two-subunit DNA escort mechanism and inactive subunit bypass in an ultra-fast ring ATPase

    Ninning Liu, Gheorghe Chistol, Carlos Bustamante
    Research Article Updated

    SpoIIIE is a homo-hexameric dsDNA translocase responsible for completing chromosome segregation in Bacillus subtilis. Here, we use a single-molecule approach to monitor SpoIIIE translocation when challenged with neutral-backbone DNA and non-hydrolyzable ATP analogs. We show that SpoIIIE makes multiple essential contacts with phosphates on the 5'→3' strand in the direction of translocation. Using DNA constructs with two neutral-backbone segments separated by a single charged base pair, we deduce that SpoIIIE’s step size is 2 bp. Finally, experiments with non-hydrolyzable ATP analogs suggest that SpoIIIE can operate with non-consecutive inactive subunits. We propose a two-subunit escort translocation mechanism that is strict enough to enable SpoIIIE to track one DNA strand, yet sufficiently compliant to permit the motor to bypass inactive subunits without arrest. We speculate that such a flexible mechanism arose for motors that, like SpoIIIE, constitute functional bottlenecks where the inactivation of even a single motor can be lethal for the cell.