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Structure of the KcsA channel intracellular gate in the open state

Nature Structural Biology volume 8, pages 883–887 (2001)Cite this article

Abstract

Ion channels catalyze the selective transfer of ions across the membrane in response to a variety of stimuli. These channels gate by controlling the access of ions to a centrally located water-filled pore. The crystal structure of the Streptomyces lividans potassium channel (KcsA) has allowed a molecular exploration of this mechanism. Electron paramagnetic resonance (EPR) studies have uncovered significant conformational changes at the intracellular end of the second transmembrane helix (TM2) upon gating. We have used site-directed spin labeling (SDSL) and EPR spectroscopy in an attempt to quantify the structural rearrangements of the KcsA TM2 bundle underlying the transition from the closed to the open state. Under conditions favoring the closed and open conformations, 10 intersubunit distances were obtained across TM2 segments from tandem dimer constructs. Analysis of these data points to a mechanism in which each TM2 helix tilts away from the permeation pathway, towards the membrane plane, and rotates about its helical axis, supporting a scissoring-type motion with a pivot point near residues 107–108. These movements are accompanied by a large increase in the diameter of the vestibule below the central water-filled cavity.

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Figure 1: Design and evaluation of KcsA tandem dimer constructs.
Figure 2: Spectral dataset from 10 spin-labeled mutants under neutral (closed state) and low pH (open state) conditions.
Figure 3: Calculated distances from 10 spin-labeled mutants in the closed and open states.
Figure 4: Modeling the conformational rearrangements in TM2.

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Acknowledgements

We thank Y.-K. Shin and W. Xiao for sharing SA/MD protocols and the algorithm for Fourier deconvolution, D.M. Cortes and L. Cuello for site-directed mutagenesis, and B. Roux and G. Yellen for discussions. This work was supported by grants from the NIH and the McKnight endowment fund for neuroscience.

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  1. Pornthep Sompornpisut: On leave from Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.

Authors and Affiliations

  1. Department of Molecular Physiology and Biological Physics, Center for Structural Biology, University of Virginia Health Sciences Center, Charlottesville, 22906-0011, Virginia, USA

    Yi-Shiuan Liu, Pornthep Sompornpisut & Eduardo Perozo

  2. Biophysics Program, University of Virginia Health Sciences Center, Charlottesville, 22906-0011, Virginia, USA

    Yi-Shiuan Liu

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  1. Yi-Shiuan Liu
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Correspondence to Eduardo Perozo.

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Liu, YS., Sompornpisut, P. & Perozo, E. Structure of the KcsA channel intracellular gate in the open state. Nat Struct Mol Biol 8, 883–887 (2001). https://doi.org/10.1038/nsb1001-883

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