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-Structure paper
タイトル | Quasi-symmetry in the cryo-EM structure of EmrE provides the key to modeling its transmembrane domain. |
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ジャーナル・号・ページ | J Mol Biol, Vol. 364, Issue 1, Page 54-67, Year 2006 |
掲載日 | 2006年11月17日 |
著者 | Sarel J Fleishman / Susan E Harrington / Angela Enosh / Dan Halperin / Christopher G Tate / Nir Ben-Tal / |
PubMed 要旨 | 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 ...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. |
リンク | J Mol Biol / PubMed:17005200 |
手法 | EM (電子線結晶学) |
解像度 | 7.5 Å |
構造データ | PDB-2i68: |
由来 |
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キーワード | TRANSPORT PROTEIN / transmembrane protein / small-multidrug resistance / transporter / homodimer / dual topology |