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Copyright © 2008 by the American Association for the Advancement of Science
A Structural Mechanism for MscS Gating in Lipid BilayersValeria Vásquez,1,2 Marcos Sotomayor,3 Julio Cordero-Morales,1,2 Klaus Schulten,4 Eduardo Perozo2* Abstract: The mechanosensitive channel of small conductance (MscS) is a key determinant in the prokaryotic response to osmotic challenges. We determined the structural rearrangements associated with MscS activation in membranes, using functorial measurements, electron paramagnetic resonance spectroscopy, and computational analyses. MscS was trapped in its open conformation after the transbilayer pressure profile was modified through the asymmetric incorporation of lysophospholipids. The transition from the closed to the open state is accompanied by the downward tilting of the transmembrane TM1-TM2 hairpin and by the expansion, tilt, and rotation of the TM3 helices. These movements expand the permeation pathway, leading to an increase in accessibility to water around TM3. Our open MscS model is compatible with single-channel conductance measurements and supports the notion that helix tilting is associated with efficient pore widening in mechanosensitive channels.
1 Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA. * To whom correspondence should be addressed. E-mail: eperozo{at}uchicago.edu
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Science Signaling. ISSN 1937-9145 (online), 1945-0877 (print). Pre-2008: Science's STKE. ISSN 1525-8882