PDBsum entry 2i0c

Membrane protein

PDB id: 2i0c

Contents

Protein chains

257 a.a.

Ligands

GLU ×2

Waters ×204

References listed in PDB file

Key reference

Title

Conformational restriction blocks glutamate receptor desensitization.

Authors

M.C.Weston, P.Schuck, A.Ghosal, C.Rosenmund, M.L.Mayer.

Ref.

Nat Struct Mol Biol, 2006, 13, 1120-1127. [DOI no: 10.1038/nsmb1178]

PubMed id

17115050

Abstract

Desensitization is a universal feature of ligand-gated ion channels. Using the crystal structure of the GluR2 L483Y mutant channel as a guide, we attempted to build non-desensitizing kainate-subtype glutamate receptors. Success was achieved for GluR5, GluR6 and GluR7 with intermolecular disulfide cross-links but not by engineering the dimer interface. Crystallographic analysis of the GluR6 Y490C L752C dimer revealed relaxation from the active conformation, which functional studies reveal is not sufficient to trigger desensitization. The equivalent non-desensitizing cross-linked GluR2 mutant retained weak sensitivity to a positive allosteric modulator, which had no effect on GluR2 L483Y. These results establish that the active conformation of AMPA and kainate receptors is conserved and further show that their desensitization requires dimer rearrangements, that subtle structural differences account for their diverse functional properties and that the ligand-binding core dimer is a powerful regulator of ion-channel activity.

Figure 4.
Figure 4. Non-desensitizing glutamate receptors created by ligand-binding core disulfide bond cross-links. Responses to 10 mM glutamate, recorded from outside-out patches from HEK cells transfected with the indicated cDNA species, are shown for wild-type GluR2 and the kainate receptors GluR5, GluR6 and GluR7 (left charts) and for their ligand-binding core double cysteine mutants (right charts). Upper traces in each panel show open-tip responses recorded at the end of the experiment.

Figure 6.
Figure 6. Analysis of disulfide bond–cross-linked receptors. (a) Crystal structure of the GluR6 Y490C L752C mutant cross-linked dimer assembly. C positions of Ser761 and Ile653 are show as black spheres at the top and bottom of each subunit, respectively. (b) Electron density for [A]-weighted F[o] – F[c] omit maps at 2.25-Å resolution, contoured at 3.25 calculated with the Y490C L752C residues omitted from the F[c] calculation. (c) Crystal structure of the GluR6 ELKQ mutant dimer, illustrating the change in separation of Ser761 and Ile653 compared with the disulfide bond–cross-linked receptor. (d) Superimposed responses to 10 mM glutamate (black bars above traces) recorded in the absence or presence of cyclothiazide (white bar; asterisks mark traces in the presence of cyclothiazide), from outside-out patches from HEK cells transfected with cDNAs for GluR2 L483C L752C (left) and GluR2 L483Y (right).

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nat Struct Mol Biol (2006, 13, 1120-1127) copyright 2006.