Mapping a molecular link between allosteric inhibition and activation of the glycine receptor.
Cys-loop ligand-gated ion channels mediate rapid neurotransmission throughout the central nervous system. They possess agonist recognition sites and allosteric sites where modulators regulate ion channel function. Using strychnine-sensitive glycine receptors, we identified a scaffold of hydrophobic residues enabling allosteric communication between glycine-agonist binding loops A and D, and the Zn(2+)-inhibition site. Mutating these hydrophobic residues disrupted Zn(2+) inhibition, generating novel Zn(2+)-activated receptors and spontaneous channel activity. Homology modeling and electrophysiology revealed that these phenomena are caused by disruption to three residues on the '-' loop face of the Zn(2+)-inhibition site, and to D84 and D86, on a neighboring beta3 strand, forming a Zn(2+)-activation site. We provide a new view for the activation of a Cys-loop receptor where, following agonist binding, the hydrophobic core and interfacial loops reorganize in a concerted fashion to induce downstream gating.
Miller
Paul S
PS
Department of Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
Topf
Maya
M
Smart
Trevor G
TG
D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D017434:Protein Structure, Tertiary; D018009:Receptors, Glycine / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D013379:Substrate Specificity; D015032:Zinc / Q000737:chemistry / Q000378:metabolism
D018009:Receptors, Glycine; D015032:Zinc