Abstract
The ligand binding domain of glutamate receptors (GluRs) has 2-fold rotational symmetry. The structure including the symmetry of the GluR ion channel remains undefined. Here we used substituted cysteines in the pore-lining M3 segment of the AMPAR GluR-A subunit and various cysteine-reactive agents to study the structure of the channel during gating. We find that cysteines substituted at A+6, located in the highly conserved SYTANLAAF motif, are grouped in pairs consistent with a 2-fold symmetry in the extracellular part of the pore. To account for this symmetry and crosslinking, we propose that the M3 segments in two neighboring GluR subunits are kinked within SYTANLAAF in opposite directions relative to the central axis of the pore. Our results extend the 2-fold rotational symmetry from the ligand binding domain to at minimum the extracellular part of the channel and suggest a model of gating movements in GluR pore-forming domains.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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6-Cyano-7-nitroquinoxaline-2,3-dione / pharmacology
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Amino Acid Motifs* / physiology
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Amino Acid Substitution / physiology
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Animals
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Binding Sites
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Cadmium / pharmacology
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Chelating Agents / pharmacology
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Conserved Sequence* / physiology
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Copper / pharmacology
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Cysteine / chemistry
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Dithiothreitol / pharmacology
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Dose-Response Relationship, Drug
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Drug Interactions
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Excitatory Amino Acid Agonists / pharmacology
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Excitatory Amino Acid Antagonists / pharmacology
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Extracellular Space* / chemistry
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Extracellular Space* / drug effects
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Extracellular Space* / physiology
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Glutamic Acid / pharmacology
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Ion Channel Gating / drug effects
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Kinetics
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Ligands
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Membrane Potentials / drug effects
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Membrane Potentials / physiology
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Microinjections
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Models, Molecular
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Oocytes
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Patch-Clamp Techniques / methods
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Phenanthrolines / pharmacology
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Protein Structure, Tertiary
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Receptors, AMPA / chemistry*
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Receptors, AMPA / physiology
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Sulfhydryl Compounds / chemistry
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Sulfhydryl Compounds / pharmacology
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Unithiol / pharmacology
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Xenopus
Substances
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Chelating Agents
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Excitatory Amino Acid Agonists
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Excitatory Amino Acid Antagonists
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Ligands
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Phenanthrolines
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Receptors, AMPA
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Sulfhydryl Compounds
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Cadmium
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Glutamic Acid
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Unithiol
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6-Cyano-7-nitroquinoxaline-2,3-dione
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Copper
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Cysteine
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Dithiothreitol