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Biophys. J. BioFAST: First Published August 19, 2005. doi:10.1529/biophysj.105.068783
© 2005 by the Biophysical Society.

A more recent version of this article appeared on November 1, 2005.
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CHANNELS, RECEPTORS, AND ELECTRICAL SIGNALING

Plasticity of Acetylcholine Receptor Gating Motions via Rate-Energy Relationships

Ananya Mitra 1, Richard Tascione 1, Anthony Auerbach 2 and Stuart Licht 1*

1 SUNY-Buffalo
2 SUNY - Buffalo

* To whom correspondence should be addressed. E-mail: lichts{at}mit.edu.

Submitted on June 14, 2005
Revised on July 21, 2005
Accepted on 26 July 2005


  Abstract
Like other protein conformational changes, ion channel gating requires the protein to achieve a high-energy transition state structure. It is not known whether ion channel gating takes place on a broad energy landscape on which many alternative transition state structures are accessible, or on a narrow energy landscape where only a few transition state structures are possible. To address this question, we measured how rate-equilibrium free energy relationships (REFERs) for diliganded and unliganded acetylcholine receptor gating vary as a function of the gating equilibrium constant. A large slope for the REFER plot indicates an "open-like" transition state, while a small slope indicates a "closed-like" transition state. Due to this relationship between REFERs and transition state structure, the sensitivity of the REFER slope to mutation-induced energetic perturbations allows estimation of the breadth of the energy landscape underlying gating. The relatively large sensitivity of diliganded REFER slopes to energetic perturbations suggests that the motions underlying diliganded gating take place on a broad, shallow energy landscape where many alternative transition state structures are accessible.

Key Words: Hammond effect, energy landscape, linear free energy relationships, protein conformational changes




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Copyright © 2005 by the Biophysical Society.