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Title: Mechanochemical coupling and bi-phasic force-velocity dependence in the ultra-fast ring ATPase SpoIIIE

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.
Authors:
ORCiD logo [1] ;  [2] ;  [3] ; ORCiD logo [4]
  1. Jason L. Choy Laboratory of Single Molecule Biophysics, University of California, Berkeley, Berkeley, United States, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
  2. Jason L. Choy Laboratory of Single Molecule Biophysics, University of California, Berkeley, Berkeley, United States, Department of Physics, University of California, Berkeley, Berkeley, United States
  3. Jason L. Choy Laboratory of Single Molecule Biophysics, University of California, Berkeley, Berkeley, United States, California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, United States
  4. Jason L. Choy Laboratory of Single Molecule Biophysics, University of California, Berkeley, Berkeley, United States, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States, Department of Physics, University of California, Berkeley, Berkeley, United States, California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, United States, Department of Chemistry and Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Published Article
Journal Name:
eLife
Additional Journal Information:
Journal Volume: 7; Related Information: CHORUS Timestamp: 2018-03-16 06:00:23; Journal ID: ISSN 2050-084X
Publisher:
eLife Sciences Publications, Ltd.
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
OSTI Identifier:
1423709
Alternate Identifier(s):
OSTI ID: 1423711