title: Role of conformational dynamics in α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor partial agonism.
abstract: We have investigated the range of cleft closure conformational states that the agonist-binding domains of the α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors occupy when bound to a series of willardiine derivatives using single-molecule FRET. These studies show that the agonist-binding domain exhibits varying degrees of dynamics when bound to the different willardiines with differing efficacies. The chlorowillardiine- and nitrowillardiine-bound form of the agonist-binding domain probes a narrower range of cleft closure states relative to the iodowillardiine bound form of the protein, with the antagonist (αS)-α-amino-3-[(4-carboxyphenyl)methyl]-3,4-dihydro-2,4-dioxo-1(2H)-pyrimidinepropanoic acid (UBP-282)-bound form exhibiting the widest range of cleft closure states. Additionally, the average cleft closure follows the order UBP-282 > iodowillardiine > chlorowillardiine > nitrowillardiine-bound forms of agonist-binding domain. These single-molecule FRET data, along with our previously reported data for the glutamate-bound forms of wild type and T686S mutant proteins, show that the mean currents under nondesensitizing conditions can be directly correlated to the fraction of the agonist-binding domains in the "closed" cleft conformation. These results indicate that channel opening in the AMPA receptors is controlled by both the ability of the agonist to induce cleft closure and the dynamics of the agonist-binding domain when bound to the agonist.
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School of Biomedical Sciences, University of Texas Health Science Center, Houston, Texas 77030, USA.
authors.forename: Swarna
authors.initials: S
authors.lastname: Ramaswamy
authors.forename: David
authors.initials: D
authors.lastname: Cooper
authors.forename: Nitesh
authors.initials: N
authors.lastname: Poddar
authors.forename: David M
authors.initials: DM
authors.lastname: MacLean
authors.forename: Anu
authors.initials: A
authors.lastname: Rambhadran
authors.forename: J Nick
authors.initials: JN
authors.lastname: Taylor
authors.forename: Heui
authors.initials: H
authors.lastname: Uhm
authors.forename: Christy F
authors.initials: CF
authors.lastname: Landes
authors.forename: Vasanthi
authors.initials: V
authors.lastname: Jayaraman
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives* / Q000737:chemistry; D019943:Amino Acid Substitution; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods; D057809:HEK293 Cells; D006801:Humans; D020125:Mutation, Missense; D017434:Protein Structure, Tertiary; D018091:Receptors, AMPA / Q000819:agonists* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014498:Uracil / Q000737:chemistry*
chemical_list: D018091:Receptors, AMPA; C002872:willardiine; D014498:Uracil; D000409:Alanine; C104722:glutamate receptor ionotropic, AMPA 2