help button home button Biophys. J.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
Biophys. J. BioFAST: First Published December 1, 2006. doi:10.1529/biophysj.106.097618
© 2006 by the Biophysical Society.

A more recent version of this article appeared on March 1, 2007.
This Article
Right arrow Full Text (Rapid PDF)
Right arrow All Versions of this Article:
biophysj.106.097618v1
92/5/1623    most recent
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Kad, N. M.
Right arrow Articles by Warshaw, D. M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Kad, N. M.
Right arrow Articles by Warshaw, D. M.

MUSCLE AND CONTRACTILITY

Mutation of a conserved glycine in the SH1-SH2 helix affects the load-dependent kinetics of myosin

Neil M. Kad 1, Joe B. Patlak 1, Patricia M. Fagnant 1, Kathleen M. Trybus 1 and David M. Warshaw 1*

1 University of Vermont

* To whom correspondence should be addressed. E-mail: warshaw{at}physiology.med.uvm.edu.

Submitted on September 19, 2006
Revised on November 6, 2006
Accepted on 14 November 2006


  Abstract
The ATP hydrolysis rate and shortening velocity of muscle are load-dependent. At the molecular level, myosin generates force and motion by coupling ATP hydrolysis to lever arm rotation. Using a laser trap to apply load to single heads of expressed smooth muscle myosin (S1), the ADP release kinetics accelerated with an assistive load, and slowed with a resistive load, however, ATP binding was mostly unaffected. To investigate how load is communicated within the motor, a glycine located at the putative fulcrum of the lever arm was mutated to valine (G709V). In the absence of load, stopped-flow and laser trap studies showed that the mutation significantly slowed the rates of ADP release and ATP binding, accounting for the ~270-fold decrease in actin sliding velocity. The load-dependence of the mutant's ADP release rate was the same as that of wild-type S1 (WT), despite the slower rate. In contrast, load accelerated ATP binding by ~20-fold, irrespective of loading direction. Imparting mechanical energy to the mutant motor partially reversed the slowed ATP-binding by overcoming the elevated activation energy barrier. These results imply that conformational changes near the conserved G709 are critical for the transmission of mechanochemical information between myosin's active site and lever arm.

Key Words: Fenn effect, force clamp, laser trap, single molecule, smooth muscle, strain dependence




This article has been cited by other articles:


Home page
 Biophys. JHome page
C. Yang, S. Ramanath, W. A. Kronert, S. I. Bernstein, D. W. Maughan, and D. M. Swank
Alternative Versions of the Myosin Relay Domain Differentially Respond to Load to Influence Drosophila Muscle Kinetics
Biophys. J., December 1, 2008; 95(11): 5228 - 5237.
[Abstract] [Full Text] [PDF]

Home page
 J. Biol. Chem.Home page
N. M. Kad, K. M. Trybus, and D. M. Warshaw
Load and Pi Control Flux through the Branched Kinetic Cycle of Myosin V
J. Biol. Chem., June 20, 2008; 283(25): 17477 - 17484.
[Abstract] [Full Text] [PDF]

Home page
 Biophys. JHome page
B. M. Palmer, T. Suzuki, Y. Wang, W. D. Barnes, M. S. Miller, and D. W. Maughan
Two-State Model of Acto-Myosin Attachment-Detachment Predicts C-Process of Sinusoidal Analysis
Biophys. J., August 1, 2007; 93(3): 760 - 769.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
Copyright © 2006 by the Biophysical Society.