Crystal Structures of a Ligand-free Mthk Gating Ring: Insights into the Ligand Gating Mechanism of K+ Channels.
From: Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Cell
- Publish Date: Sep 2006
- ISSN: 0092-8674
- Volume: 126
- Issue: 6
- Pages: 1161-73
- Medium: Print
- Language: English
- Citation (JAMA): Ye Sheng, Li Yang, Chen Liping, et al. Crystal Structures of a Ligand-free Mthk Gating Ring: Insights into the Ligand Gating Mechanism of K+ Channels.. Cell Sep 2006;126:1161-73
Abstract
MthK is a prokaryotic Ca(2+)-gated K(+) channel that, like other ligand-gated channels, converts the chemical energy of ligand binding to the mechanical force of channel opening. The channel’s eight ligand-binding domains, the RCK domains, form an octameric gating ring in which Ca(2+) binding induces conformational changes that open the channel. Here we present the crystal structures of the MthK gating ring in closed and partially open states at 2.8 A, both obtained from the same crystal grown in the absence of Ca(2+). Furthermore, our biochemical and electrophysiological analyses demonstrate that MthK is regulated by both Ca(2+) and pH. Ca(2+) regulates the channel by changing the equilibrium of the gating ring between closed and open states, while pH regulates channel gating by affecting gating-ring stability. Our findings, along with the previously determined open MthK structure, allow us to elucidate the ligand gating mechanism of RCK-regulated K(+) channels.
Mesh Headings (Keywords): Allosteric Regulation, Bacteria, Binding Sites, Calcium, Calcium Signaling, Cell Membrane, Crystallography, X-Ray, Dimerization, Ion Channel Gating, Ligands, Membrane Potentials, Models, Molecular, Potassium, Potassium Channels, Calcium-Activated, Protein Structure, Quaternary, Protein Subunits, Signal Transduction
Check for Full Text / PubMed Unique Identifier (PMID): 16990139
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The data herein was last updated on July 8th, 2008 and may not reflect the most current and accurate data available from NLM.