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Biophys. J. BioFAST: First Published January 21, 2005. doi:10.1529/biophysj.104.053546
© 2005 by the Biophysical Society.

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ELECTROPHYSIOLOGY

Surface changes of the mechanosensitive channel MscS upon its activation, inactivation and closing

Wojciech Grajkowski 1, Andrzej Kubalski 1* and Piotr Koprowski 1

1 Nencki Institute of Experimental Biology

* To whom correspondence should be addressed. E-mail: kubalski{at}nencki.gov.pl.

Submitted on September 29, 2004
Revised on October 29, 2004
Accepted on 5 January 2005


  Abstract
MscS is a bacterial mechanosensitive (MS) channel that shows voltage dependence. The crystal structure of MscS revealed that the channel is a homoheptamer with a large chamber on the intracellular site. Our previous experiments indicated that the cytoplasmic chamber of the channel is not a rigid structure, and changes its conformation upon the channel activation.In this study we have applied various-size cosolvents that are excluded from protein surfaces. It is well known that such cosolvents induce compaction of proteins and prevent thermal fluctuations. It is also known that they shift channel equilibrium to the state of lower volume. We have found that large cosolvents that cannot enter the channel interior accelerate channel inactivation when applied from the cytoplasmic side but they slow down inactivation when applied from the extracellular side. We have also found that small cosolvents that can enter the channel cytoplasmic chamber prevent the channel from opening unlike the large ones. These data support our idea that the channel cytoplasmic chamber shrinks upon inactivation but also give new clues on conformational changes of the channel upon transitions between its functional states.

Key Words: cosolvent, gating, mechanosensitive channel, preferential exclusion




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Copyright © 2005 by the Biophysical Society.