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Biophys. J. BioFAST: First Published March 24, 2006. doi:10.1529/biophysj.105.073254
© 2006 by the Biophysical Society.

A more recent version of this article appeared on June 1, 2006.
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CHANNELS, RECEPTORS, AND ELECTRICAL SIGNALING

An Anion Antiporter Model of Prestin, the Outer Hair Cell Motor Protein

Daniella R Muallem 1 and Jonathan F. Ashmore 1*

1 University College London

* To whom correspondence should be addressed. E-mail: j.ashmore{at}ucl.ac.uk.

Submitted on August 26, 2005
Revised on September 26, 2005
Accepted on 27 February 2006


  Abstract
Cochlear amplification in mammalian hearing relies on an active mechanical feedback process generated by outer hair cells (OHCs), driven by a protein, prestin (SLC26A5), in the lateral membrane. We have used kinetic models to understand the mechanism by which prestin might function. We show that the two previous hypotheses of prestin, which assume prestin cannot operate as a transporter, are insufficient to explain previously published data. We propose an alternative model of prestin as an electrogenic anion exchanger, exchanging one Cl- ion for one divalent or two monovalent anions. This model can reproduce the key aspects of previous experimental observations. The experimentally observed charge movements are produced by the translocation of one Cl- ion combined with intrinsic positively charged residues, whilst the transport of the counter-anion is electroneutral. We tested the model with measurements of the Cl- dependence of charge movement, using SO42- to replace Cl-. The data was compatible with the predictions of the model, suggesting that prestin does indeed function as a transporter.

Key Words: OHC, SLC26, chloride transporter, cochlea, electromotility, kinetic model




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Copyright © 2006 by the Biophysical Society.