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Ionotropic glutamate receptors are essential for fast synaptic nerve transmission. Recent x-ray structures for the ligand-binding (S1S2) region of the GluR2 alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-sensitive receptor have suggested how differences in protein/ligand interactions may determine whether a ligand will behave as a full agonist. We have used multiple molecular dynamics simulations of 2-5 ns duration to explore the structural dynamics of GluR2 S1S2 in the presence and absence of glutamate and in a complex with kainate. Our studies indicate that not only is the degree of domain closure dependent upon interactions with the ligand, but also that protein/ligand interactions influence the motion of the S2 domain with respect to S1. Differences in domain mobility between the three states (apo-S1S2, glutamate-bound, and kainate-bound) are surprisingly clear-cut. We discuss how these changes in dynamics may provide an explanation relating the mechanism of transmission of the agonist-binding event to channel opening. We also show here how the glutamate may adopt an alternative mode of binding not seen in the x-ray structure, which involves a key threonine (T480) side chain flipping into a new conformation. This new conformation results in an altered pattern of hydrogen bonding at the agonist-binding site.

Original publication

DOI

10.1016/S0006-3495(02)75430-1

Type

Journal article

Journal

Biophys J

Publication Date

02/2002

Volume

82

Pages

676 - 683

Keywords

Algorithms, Apolipoprotein A-II, Binding Sites, Computer Simulation, Crystallography, X-Ray, Glutamic Acid, Hydrogen Bonding, Hydrogen-Ion Concentration, Kainic Acid, Ligands, Models, Molecular, Peptides, Protein Binding, Protein Conformation, Protein Structure, Tertiary, Receptors, AMPA, Threonine, Time Factors