CHANNELS, RECEPTORS, AND ELECTRICAL SIGNALING |
Interaction between the cytoplasmic and transmembrane domains of the mechanosensitive channel, MscS
Takeshi Nomura 1, Masahiro Sokabe 2 and Kenjiro Yoshimura 3*
1 JST
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 June 11, 2007
Revised on July 5, 2007
Accepted on 22 October 2007
 |
Abstract |
|---|
The bacterial mechanosensitive channel, MscS, protects the bacteria from rupture on hypoosmotic shock. MscS is composed of a transmembrane domain with an ion permeation pore and a large cytoplasmic vestibule that undergoes significant conformational changes upon gating. In this study, we investigated whether specific residues in the transmembrane and cytoplasmic domains of MscS influence each other during gating. When Asp-62, a negatively charged residue located in the loop that connects the first and second transmembrane helices, was substituted with either a neutral (Cys or Asn) or basic (Arg) amino acid, an increase in both the gating threshold and inactivation rate was observed. Similar effects were observed after neutralization or reversal of the charge of either Arg-128 or Arg-131, which are located near Asp-62 on the upper surface of the cytoplasmic domain. Interestingly, the effects of the substitution of Asp-62 with arginine were complemented by reversing the charge of Arg-131. Complementation was not observed after simultaneous neutralization of the charge of these residues. These findings suggest that the cytoplasmic domain of MscS affects both the mechanosensitive gating and the channel inactivation rate through the electrostatic interaction between Asp-62 and Arg-131.
Key Words:
E. coli, electrostatic interaction, inactivation, ion channel, osmotic shock, patch clamp
