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- Title
Pivotal role of the glycine-rich TM3 helix in gating the MscS mechanosensitive channel.
- Authors
Edwards, Michelle D; Li, Yuezhou; Kim, Sanguk; Miller, Samantha; Bartlett, Wendy; Black, Susan; Dennison, Sally; Iscla, Irene; Blount, Paul; Bowie, James U; Booth, Ian R
- Abstract
The crystal structure of an open form of the Escherichia coli MscS mechanosensitive channel was recently solved. However, the conformation of the closed state and the gating transition remain uncharacterized. The pore-lining transmembrane helix contains a conserved glycine- and alanine-rich motif that forms a helix-helix interface. We show that introducing 'knobs' on the smooth glycine face by replacing glycine with alanine, and substituting conserved alanines with larger residues, increases the pressure required for gating. Creation of a glycine-glycine interface lowers activation pressure. The importance of residues Gly104, Ala106 and Gly108, which flank the hydrophobic seal, is demonstrated. A new structural model is proposed for the closed-to-open transition that involves rotation and tilt of the pore-lining helices. Introduction of glycine at Ala106 validated this model by acting as a powerful suppressor of defects seen with mutations at Gly104 and Gly108.
- Publication
Nature structural & molecular biology, 2005, Vol 12, Issue 2, p113
- ISSN
1545-9993
- Publication type
Journal Article
- DOI
10.1038/nsmb895