Document Detail

The speed of the flagellar rotary motor of Escherichia coli varies linearly with protonmotive force.
MedLine Citation:
PMID:  12857945     Owner:  NLM     Status:  MEDLINE    
A protonmotive force (pmf) across the cell's inner membrane powers the flagellar rotary motor of Escherichia coli. Speed is known to be proportional to pmf when viscous loads are heavy. Here we show that speed also is proportional to pmf when viscous loads are light. Two motors on the same bacterium were monitored as the cell was slowly deenergized. The first motor rotated the entire cell body (a heavy load), while the second motor rotated a small latex bead (a light load). The first motor rotated slowly and provided a measure of the cell's pmf. The second motor rotated rapidly and was compared with the first, to give the speed-pmf relation for light loads. Experiments were done at 24.0 degrees C and 16.2 degrees C, with initial speeds indicating operation well into the high-speed, low-torque regime. Speed was found to be proportional to pmf over the entire (accessible) dynamic range (0-270 Hz). If the passage of a fixed number of protons carries the motor through each revolution, i.e., if the motor is tightly coupled, a linear speed-pmf relation is expected close to stall, where the work done against the viscous load matches the energy dissipated in proton flow. A linear relation is expected at high speeds if proton translocation is rate-limiting and involves multiple steps, a model that also applies to simple proton channels. The present work shows that a linear relation is true more generally, providing an additional constraint on possible motor mechanisms.
Christopher V Gabel; Howard C Berg
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.     Date:  2003-07-11
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  100     ISSN:  0027-8424     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2003 Jul 
Date Detail:
Created Date:  2003-07-23     Completed Date:  2003-09-02     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  8748-51     Citation Subset:  IM    
Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
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MeSH Terms
Biophysical Phenomena
Escherichia coli / physiology*
Escherichia coli Proteins / physiology
Flagella / physiology*
Ion Channels / physiology
Molecular Motor Proteins / physiology*
Movement / physiology
Proton-Motive Force
Grant Support
Reg. No./Substance:
0/Escherichia coli Proteins; 0/Ion Channels; 0/Molecular Motor Proteins

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