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[[Image:1mxw.gif|left|200px]]<br /><applet load="1mxw" size="350" color="white" frame="true" align="right" spinBox="true"
caption="1mxw, resolution 1.90&Aring;" />
'''crystal titration experiments (AMPA co-crystals soaked in 1 mM BrW)'''<br />


==Overview==
==crystal titration experiments (AMPA co-crystals soaked in 1 mM BrW)==
An unresolved problem in understanding neurotransmitter receptor function concerns the mechanism(s) by which full and partial agonists elicit different amplitude responses at equal receptor occupancy. The widely held view of 'partial agonism' posits that resting and active states of the receptor are in equilibrium, and partial agonists simply do not shift the equilibrium toward the active state as efficaciously as full agonists. Here we report findings from crystallographic and electrophysiological studies of the mechanism of activation of an AMPA-subtype glutamate receptor ion channel. In these experiments, we used 5-substituted willardiines, a series of partial agonists that differ by only a single atom. Our results show that the GluR2 ligand-binding core can adopt a range of ligand-dependent conformational states, which in turn control the open probability of discrete subconductance states of the intact ion channel. Our findings thus provide a structure-based model of partial agonism.
<StructureSection load='1mxw' size='340' side='right'caption='[[1mxw]], [[Resolution|resolution]] 1.90&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1mxw]] is a 3 chain structure with sequence from [https://en.wikipedia.org/wiki/Rattus_norvegicus Rattus norvegicus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1MXW OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1MXW FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.9&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ZN:ZINC+ION'>ZN</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1mxw FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1mxw OCA], [https://pdbe.org/1mxw PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1mxw RCSB], [https://www.ebi.ac.uk/pdbsum/1mxw PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1mxw ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/GRIA2_RAT GRIA2_RAT] Receptor for glutamate that functions as ligand-gated ion channel in the central nervous system and plays an important role in excitatory synaptic transmission. L-glutamate acts as an excitatory neurotransmitter at many synapses in the central nervous system. Binding of the excitatory neurotransmitter L-glutamate induces a conformation change, leading to the opening of the cation channel, and thereby converts the chemical signal to an electrical impulse. The receptor then desensitizes rapidly and enters a transient inactive state, characterized by the presence of bound agonist. In the presence of CACNG4 or CACNG7 or CACNG8, shows resensitization which is characterized by a delayed accumulation of current flux upon continued application of glutamate.<ref>PMID:9351977</ref> <ref>PMID:19265014</ref> <ref>PMID:21172611</ref> <ref>PMID:12501192</ref> <ref>PMID:12015593</ref> <ref>PMID:12872125</ref> <ref>PMID:12730367</ref> <ref>PMID:16192394</ref> <ref>PMID:15591246</ref> <ref>PMID:17018279</ref> <ref>PMID:16483599</ref> <ref>PMID:19946266</ref> <ref>PMID:21317873</ref> <ref>PMID:21846932</ref>
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/mx/1mxw_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview03.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=1mxw ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Numerous naturally occurring and synthetic alpha-amino acids act as agonists on (S)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazole) propionic acid (AMPA) receptors but nevertheless display significant differences in their functional properties and modes of interaction. The 5-substituted willardiines are a series of compounds that exhibit a range of affinities, act as partial agonists, and give rise to intermediate levels of activation and desensitization. However, the molecular basis for the activities of 5-substituted willardiines has not been conclusively elaborated at the level of atomic resolution. Here we provide insight into the molecular basis of the potency and efficacy elicited by the 5-substituted willardiines on the basis of cocrystal structures with the GluR2 ligand-binding core. We also show that the crystallized ligand-binding core has an affinity for agonists similar to the ligand-binding core in solution. Analysis of multiple crystal lattices suggests modes by which the ligand-binding core dimers interact in the tetrameric receptor. These studies further our understanding of how subtle differences in the structures of agonists are correlated to changes in the conformation of residues and water molecules in the immediate binding pocket and to the degree of domain closure.


==About this Structure==
Probing the function, conformational plasticity, and dimer-dimer contacts of the GluR2 ligand-binding core: studies of 5-substituted willardiines and GluR2 S1S2 in the crystal.,Jin R, Gouaux E Biochemistry. 2003 May 13;42(18):5201-13. PMID:12731861<ref>PMID:12731861</ref>
1MXW is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Rattus_norvegicus Rattus norvegicus] with <scene name='pdbligand=ZN:'>ZN</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1MXW OCA].


==Reference==
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
Structural basis for partial agonist action at ionotropic glutamate receptors., Jin R, Banke TG, Mayer ML, Traynelis SF, Gouaux E, Nat Neurosci. 2003 Aug;6(8):803-10. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=12872125 12872125]
</div>
<div class="pdbe-citations 1mxw" style="background-color:#fffaf0;"></div>
 
==See Also==
*[[Glutamate receptor 3D structures|Glutamate receptor 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Rattus norvegicus]]
[[Category: Rattus norvegicus]]
[[Category: Single protein]]
[[Category: Gouaux E]]
[[Category: Gouaux, E.]]
[[Category: Jin R]]
[[Category: Jin, R.]]
[[Category: ZN]]
[[Category: ampa]]
[[Category: bromo-willardiine]]
[[Category: crystal titration]]
[[Category: glur2]]
[[Category: ionotropic glutamate receptor]]
[[Category: ligand binding core]]
[[Category: partial agonist]]
[[Category: s1s2]]
 
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