Mechanosensitive channel gating transitions resolved by functional changes upon pore modification

Jessica L. Bartlett, Yuezhou Li, Paul Blount

Research output: Contribution to journalArticle

28 Scopus citations

Abstract

The mechanosensitive channel of large conductance acts as a biological "emergency release valve" that protects bacterial cells from hypoosmotic stress. Although structural and functional studies and molecular dynamic simulations of this channel have led to several models for the structural transitions that occur in the gating process, inconsistencies linger and details are lacking. A previous study, using a method coined as the "in vivo SCAM", identified several residues in the channel pore that were exposed to the aqueous environment in the closed and opening conformations. Briefly, the sulfhydryl reagent MTSET was allowed to react, in the presence or absence of hypoosmotic shock, with cells expressing mechanosensitive channel of large conductance channels that contained cysteine substitutions; channel dysfunction was assessed solely by cell viability. Here we evaluate the MTSET-induced functional modifications to these mechanosensitive channel activities by measuring single channel recordings. The observed changes in residue availability in different states, as well as channel kinetics and sensitivity, have allowed us to elucidate the microenvironment encountered for a number of pore residues, thus testing many aspects of previous models and giving a higher resolution of the pore domain and the structural transitions it undergoes from the closed to open state.

Original languageEnglish (US)
Pages (from-to)3684-3691
Number of pages8
JournalBiophysical Journal
Volume91
Issue number10
DOIs
Publication statusPublished - Nov 2006

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ASJC Scopus subject areas

  • Biophysics

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