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Biophys. J. BioFAST: First Published July 21, 2006. doi:10.1529/biophysj.106.084541
© 2006 by the Biophysical Society.

A more recent version of this article appeared on October 15, 2006.
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CHANNELS, RECEPTORS, AND ELECTRICAL SIGNALING

Lipid-protein interaction of the MscS mechanosensitive channel examined by scanning mutagenesis

Nomura Takeshi 1, Masahiro Sokabe 2 and Kenjiro Yoshimura 3*

1 Japan Science and Technology Agency
2 Nagoya University Graduate School of Medicine
3 University of Tsukuba

* To whom correspondence should be addressed. E-mail: kenjiro{at}biol.tsukuba.ac.jp.

Submitted on March 8, 2006
Revised on April 5, 2006
Accepted on 10 July 2006


  Abstract
The mechanosensitive channel of small conductance (MscS) is a bacterial mechanosensitive channel that opens in response to rapid hypoosmotic stress. Since MscS can be opened solely by membrane stretch without help from any accessory protein, the lipid-protein interface must play a crucial role in sensing membrane tension. In the present study, the hydrophobic residues in the lipid-protein interface were substituted one by one with a hydrophilic amino acid, asparagine, to modify the interaction between the protein and the lipid. Function of the mutant MscSs was examined by patch-clamp and hypoosmotic shock experiments. An increase in the gating threshold and a decrease in the viability on hypoosmotic shock were observed when the hydrophobic residues near either end of the first or the second transmembrane helix (TM1 or TM2) were replaced with asparagine. This observation indicates that the lipid-protein interaction at the ends of both helices (TM1 and TM2) is essential to MscS function.

Key Words: E. coli, electrophysiology, hydrophobic mismatch, ion channel, patch clamp




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Copyright © 2006 by the Biophysical Society.