Crystal structure and mechanism of a calcium-gated potassium channel

Ion channels exhibit two essential biophysical properties; that is, selective ion conduction, and the ability to gate-open in response to an appropriate stimulus. Two general categories of ion channel gating are defined by the initiating stimulus: ligand binding (neurotransmitter- or second-messenger-gated channels) or membrane voltage (voltage-gated channels). Here we present the structural basis of ligand gating in a K+ channel that opens in response to intracellular Ca2+. We have cloned, expressed, analysed electrical properties, and determined the crystal structure of a K+ channel (MthK) from Methanobacterium thermoautotrophicum in the Ca2+-bound, opened state. Eight RCK domains (regulators of K+ conductance) form a gating ring at the intracellular membrane surface. The gating ring uses the free energy of Ca2+ binding in a simple manner to perform mechanical work to open the pore.

[1]  Youxing Jiang,et al.  Structure of the RCK Domain from the E. coli K+ Channel and Demonstration of Its Presence in the Human BK Channel , 2001, Neuron.

[2]  L. Salkoff,et al.  A novel calcium-sensing domain in the BK channel. , 1997, Biophysical journal.

[3]  F J Sigworth,et al.  Voltage gating of ion channels , 1994, Quarterly Reviews of Biophysics.

[4]  F. Quiocho,et al.  Periplasmic binding protein structure and function. Refined X-ray structures of the leucine/isoleucine/valine-binding protein and its complex with leucine. , 1989, Journal of molecular biology.

[5]  R. MacKinnon,et al.  Chemistry of ion coordination and hydration revealed by a K+ channel–Fab complex at 2.0 Å resolution , 2001, Nature.

[6]  J. Zou,et al.  The 1.7 A refined X-ray structure of the periplasmic glucose/galactose receptor from Salmonella typhimurium. , 1993, Journal of molecular biology.

[7]  R. MacKinnon,et al.  Mutant potassium channels with altered binding of charybdotoxin, a pore-blocking peptide inhibitor. , 1989, Science.

[8]  G. Thomas,et al.  Bi-cycling the furin pathway: from TGN localization to pathogen activation and embryogenesis. , 1999, Trends in cell biology.

[9]  D. H. Cox,et al.  Separation of Gating Properties from Permeation and Block in mslo Large Conductance Ca-activated K+ Channels , 1997, The Journal of general physiology.

[10]  G. Bricogne,et al.  [27] Maximum-likelihood heavy-atom parameter refinement for multiple isomorphous replacement and multiwavelength anomalous diffraction methods. , 1997, Methods in enzymology.

[11]  D. Bossemeyer,et al.  NAD+ binding to the Escherichia coli K+‐uptake protein TrkA and sequence similarity between TrkA and domains of a family of dehydrogenases suggest a role for NAD+ in bacterial transport , 1993, Molecular microbiology.

[12]  S L Mowbray,et al.  Probing protein-protein interactions. The ribose-binding protein in bacterial transport and chemotaxis. , 1994, The Journal of biological chemistry.

[13]  B. Chait,et al.  Mass spectrometry as a tool for protein crystallography. , 2001, Annual review of biophysics and biomolecular structure.

[14]  Russ Miller,et al.  The design and implementation of SnB version 2.0 , 1999 .

[15]  F Bezanilla,et al.  The voltage sensor in voltage-dependent ion channels. , 2000, Physiological reviews.

[16]  R J Read,et al.  Crystallography & NMR system: A new software suite for macromolecular structure determination. , 1998, Acta crystallographica. Section D, Biological crystallography.

[17]  R Latorre,et al.  Gating kinetics of Ca2+-activated K+ channels from rat muscle incorporated into planar lipid bilayers. Evidence for two voltage- dependent Ca2+ binding reactions , 1983, The Journal of general physiology.

[18]  R Olson,et al.  Mechanisms for ligand binding to GluR0 ion channels: crystal structures of the glutamate and serine complexes and a closed apo state. , 2001, Journal of molecular biology.

[19]  T. Ishii,et al.  Mechanism of calcium gating in small-conductance calcium-activated potassium channels , 1998, Nature.

[20]  Christopher Miller,et al.  Single Streptomyces lividans K+ Channels: Functional Asymmetries and Sidedness of Proton Activation , 1999 .

[21]  M. Cadene,et al.  A robust, detergent-friendly method for mass spectrometric analysis of integral membrane proteins. , 2000, Analytical chemistry.

[22]  Z. Otwinowski,et al.  Processing of X-ray diffraction data collected in oscillation mode. , 1997, Methods in enzymology.

[23]  Collaborative Computational,et al.  The CCP4 suite: programs for protein crystallography. , 1994, Acta crystallographica. Section D, Biological crystallography.

[24]  Roderick MacKinnon,et al.  Energetic optimization of ion conduction rate by the K+ selectivity filter , 2001, Nature.

[25]  K Cowtan,et al.  Modified phased translation functions and their application to molecular-fragment location. , 1998, Acta crystallographica. Section D, Biological crystallography.

[26]  Structure and function of cyclic nucleotide-gated channels. , 1996, Annual review of neuroscience.

[27]  E. Gouaux,et al.  Structure of a glutamate-receptor ligand-binding core in complex with kainate , 1998, Nature.

[28]  C. Bellamacina.  The nicotinamide dinucleotide binding motif: a comparison of nucleotide binding proteins , 1996, FASEB journal : official publication of the Federation of American Societies for Experimental Biology.

[29]  K. Yau,et al.  Cyclic nucleotide-gated ion channels: an extended family with diverse functions. , 1996, Annual review of physiology.

[30]  R. Latorre,et al.  Kinetics of Ca2+-activated K+ channels from rabbit muscle incorporated into planar bilayers. Evidence for a Ca2+ and Ba2+ blockade , 1983, The Journal of general physiology.

[31]  B. Hille,et al.  Ionic channels of excitable membranes , 2001 .

[32]  J. Abrahams,et al.  Methods used in the structure determination of bovine mitochondrial F1 ATPase. , 1996, Acta crystallographica. Section D, Biological crystallography.

[33]  J. Golowasch,et al.  Allosteric effects of Mg2+ on the gating of Ca2+-activated K+ channels from mammalian skeletal muscle. , 1986, The Journal of experimental biology.

[34]  Youxing Jiang,et al.  The open pore conformation of potassium channels , 2002, Nature.

[35]  K. Sharp,et al.  Protein folding and association: Insights from the interfacial and thermodynamic properties of hydrocarbons , 1991, Proteins.

[36]  J. Zou,et al.  Improved methods for building protein models in electron density maps and the location of errors in these models. , 1991, Acta crystallographica. Section A, Foundations of crystallography.

[37]  R. Latorre,et al.  Charybdotoxin, a protein inhibitor of single Ca2+-activated K+ channels from mammalian skeletal muscle , 1985, Nature.

[38]  R M Esnouf,et al.  An extensively modified version of MolScript that includes greatly enhanced coloring capabilities. , 1997, Journal of molecular graphics & modelling.

[39]  Thomas C. Terwilliger,et al.  Automated MAD and MIR structure solution , 1999, Acta crystallographica. Section D, Biological crystallography.

[40]  B. Chait,et al.  The structure of the potassium channel: molecular basis of K+ conduction and selectivity. , 1998, Science.