2yvy
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(New page: 200px<br /><applet load="2yvy" size="350" color="white" frame="true" align="right" spinBox="true" caption="2yvy, resolution 2.30Å" /> '''Crystal structure of...)
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Revision as of 09:04, 23 January 2008
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Crystal structure of magnesium transporter MgtE cytosolic domain, Mg2+ bound form
Overview
The magnesium ion Mg2+ is a vital element involved in numerous, physiological processes. Mg2+ has the largest hydrated radius among all, cations, whereas its ionic radius is the smallest. It remains obscure how, Mg2+ transporters selectively recognize and dehydrate the large, fully, hydrated Mg2+ cation for transport. Recently the crystal structures of the, CorA Mg2+ transporter were reported. The MgtE family of Mg2+ transporters, is ubiquitously distributed in all phylogenetic domains, and human, homologues have been functionally characterized and suggested to be, involved in magnesium homeostasis. However, the MgtE transporters have not, been thoroughly characterized. Here we determine the crystal structures of, the full-length Thermus thermophilus MgtE at 3.5 A resolution, and of the, cytosolic domain in the presence and absence of Mg2+ at 2.3 A and 3.9 A, resolutions, respectively. The transporter adopts a homodimeric, architecture, consisting of the carboxy-terminal five transmembrane, domains and the amino-terminal cytosolic domains, which are composed of, the superhelical N domain and tandemly repeated, cystathionine-beta-synthase domains. A solvent-accessible pore nearly, traverses the transmembrane domains, with one potential Mg2+ bound to the, conserved Asp 432 within the pore. The transmembrane (TM)5 helices from, both subunits close the pore through interactions with the 'connecting, helices', which connect the cystathionine-beta-synthase and transmembrane, domains. Four putative Mg2+ ions are bound at the interface between the, connecting helices and the other domains, and this may lock the closed, conformation of the pore. A structural comparison of the two states of the, cytosolic domains showed the Mg2+-dependent movement of the connecting, helices, which might reorganize the transmembrane helices to open the, pore. These findings suggest a homeostasis mechanism, in which Mg2+ bound, between cytosolic domains regulates Mg2+ flux by sensing the intracellular, Mg2+ concentration. Whether this presumed regulation controls gating of an, ion channel or opening of a secondary active transporter remains to be, determined.
About this Structure
2YVY is a Single protein structure of sequence from Thermus thermophilus with as ligand. Full crystallographic information is available from OCA.
Reference
Crystal structure of the MgtE Mg2+ transporter., Hattori M, Tanaka Y, Fukai S, Ishitani R, Nureki O, Nature. 2007 Aug 30;448(7157):1072-5. Epub 2007 Aug 15. PMID:17700703
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