View source for 1ii5

[[Image:1ii5.gif|left|200px]]

 {{Structure
|PDB= 1ii5 |SIZE=350|CAPTION= <scene name='initialview01'>1ii5</scene>, resolution 1.60&Aring;
|SITE= 
|LIGAND= <scene name='pdbligand=GLU:GLUTAMIC ACID'>GLU</scene>
|ACTIVITY= 
|GENE= GluR0 slr1257 ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=1143 Synechocystis sp.])
}}

'''CRYSTAL STRUCTURE OF THE GLUR0 LIGAND BINDING CORE COMPLEX WITH L-GLUTAMATE'''


==Overview==
High-resolution structures of the ligand binding core of GluR0, a glutamate receptor ion channel from Synechocystis PCC 6803, have been solved by X-ray diffraction. The GluR0 structures reveal homology with bacterial periplasmic binding proteins and the rat GluR2 AMPA subtype neurotransmitter receptor. The ligand binding site is formed by a cleft between two globular alpha/beta domains. L-Glutamate binds in an extended conformation, similar to that observed for glutamine binding protein (GlnBP). However, the L-glutamate gamma-carboxyl group interacts exclusively with Asn51 in domain 1, different from the interactions of ligand with domain 2 residues observed for GluR2 and GlnBP. To address how neutral amino acids activate GluR0 gating we solved the structure of the binding site complex with L-serine. This revealed solvent molecules acting as surrogate ligand atoms, such that the serine OH group makes solvent-mediated hydrogen bonds with Asn51. The structure of a ligand-free, closed-cleft conformation revealed an extensive hydrogen bond network mediated by solvent molecules. Equilibrium centrifugation analysis revealed dimerization of the GluR0 ligand binding core with a dissociation constant of 0.8 microM. In the crystal, a symmetrical dimer involving residues in domain 1 occurs along a crystallographic 2-fold axis and suggests that tetrameric glutamate receptor ion channels are assembled from dimers of dimers. We propose that ligand-induced conformational changes cause the ion channel to open as a result of an increase in domain 2 separation relative to the dimer interface.

==About this Structure==
1II5 is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Synechocystis_sp. Synechocystis sp.]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1II5 OCA]. 

==Reference==
Mechanisms for ligand binding to GluR0 ion channels: crystal structures of the glutamate and serine complexes and a closed apo state., Mayer ML, Olson R, Gouaux E, J Mol Biol. 2001 Aug 24;311(4):815-36. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/11518533 11518533]
[[Category: Single protein]]
[[Category: Synechocystis sp.]]
[[Category: Gouaux, E.]]
[[Category: Mayer, M L.]]
[[Category: Olson, R.]]
[[Category: GLU]]
[[Category: membrane protein]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Mar 20 11:50:41 2008''