2i68
From Proteopedia
(New page: 200px<br /><applet load="2i68" size="450" color="white" frame="true" align="right" spinBox="true" caption="2i68" /> '''Cryo-EM based theoretical model structure of...) |
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'''Cryo-EM based theoretical model structure of transmembrane domain of the multidrug-resistance antiporter from E. coli EmrE'''<br /> | '''Cryo-EM based theoretical model structure of transmembrane domain of the multidrug-resistance antiporter from E. coli EmrE'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Small multidrug resistance (SMR) transporters contribute to bacterial | + | Small multidrug resistance (SMR) transporters contribute to bacterial resistance by coupling the efflux of a wide range of toxic aromatic cations, some of which are commonly used as antibiotics and antiseptics, to proton influx. EmrE is a prototypical small multidrug resistance transporter comprising four transmembrane segments (M1-M4) that forms dimers. It was suggested recently that EmrE molecules in the dimer have different topologies, i.e. monomers have opposite orientations with respect to the membrane plane. A 3-D structure of EmrE acquired by electron cryo-microscopy (cryo-EM) at 7.5 Angstroms resolution in the membrane plane showed that parts of the structure are related by quasi-symmetry. We used this symmetry relationship, combined with sequence conservation data, to assign the transmembrane segments in EmrE to the densities seen in the cryo-EM structure. A C alpha model of the transmembrane region was constructed by considering the evolutionary conservation pattern of each helix. The model is validated by much of the biochemical data on EmrE with most of the positions that were identified as affecting substrate translocation being located around the substrate-binding cavity. A suggested mechanism for proton-coupled substrate translocation in small multidrug resistance antiporters provides a mechanistic rationale to the experimentally observed inverted topology. |
==About this Structure== | ==About this Structure== | ||
| - | 2I68 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http:// | + | 2I68 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2I68 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Ben-Tal, N.]] | [[Category: Ben-Tal, N.]] | ||
[[Category: Enosh, A.]] | [[Category: Enosh, A.]] | ||
| - | [[Category: Fleishman, S | + | [[Category: Fleishman, S J.]] |
[[Category: Halperin, D.]] | [[Category: Halperin, D.]] | ||
| - | [[Category: Harrington, S | + | [[Category: Harrington, S E.]] |
| - | [[Category: Tate, C | + | [[Category: Tate, C G.]] |
[[Category: dual topology]] | [[Category: dual topology]] | ||
[[Category: homodimer]] | [[Category: homodimer]] | ||
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[[Category: transporter]] | [[Category: transporter]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 17:49:30 2008'' |
Revision as of 15:49, 21 February 2008
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Cryo-EM based theoretical model structure of transmembrane domain of the multidrug-resistance antiporter from E. coli EmrE
Overview
Small multidrug resistance (SMR) transporters contribute to bacterial resistance by coupling the efflux of a wide range of toxic aromatic cations, some of which are commonly used as antibiotics and antiseptics, to proton influx. EmrE is a prototypical small multidrug resistance transporter comprising four transmembrane segments (M1-M4) that forms dimers. It was suggested recently that EmrE molecules in the dimer have different topologies, i.e. monomers have opposite orientations with respect to the membrane plane. A 3-D structure of EmrE acquired by electron cryo-microscopy (cryo-EM) at 7.5 Angstroms resolution in the membrane plane showed that parts of the structure are related by quasi-symmetry. We used this symmetry relationship, combined with sequence conservation data, to assign the transmembrane segments in EmrE to the densities seen in the cryo-EM structure. A C alpha model of the transmembrane region was constructed by considering the evolutionary conservation pattern of each helix. The model is validated by much of the biochemical data on EmrE with most of the positions that were identified as affecting substrate translocation being located around the substrate-binding cavity. A suggested mechanism for proton-coupled substrate translocation in small multidrug resistance antiporters provides a mechanistic rationale to the experimentally observed inverted topology.
About this Structure
2I68 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Quasi-symmetry in the cryo-EM structure of EmrE provides the key to modeling its transmembrane domain., Fleishman SJ, Harrington SE, Enosh A, Halperin D, Tate CG, Ben-Tal N, J Mol Biol. 2006 Nov 17;364(1):54-67. Epub 2006 Aug 30. PMID:17005200
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