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基本情報
登録情報 | データベース: PDB / ID: 2i68 | ||||||
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タイトル | Cryo-EM based theoretical model structure of transmembrane domain of the multidrug-resistance antiporter from E. coli EmrE | ||||||
![]() | Protein emrE | ||||||
![]() | TRANSPORT PROTEIN / transmembrane protein / small-multidrug resistance / transporter / homodimer / dual topology | ||||||
機能・相同性 | ![]() EmrE multidrug transporter complex / amino-acid betaine transmembrane transporter activity / glycine betaine transport / choline transmembrane transporter activity / choline transport / xenobiotic detoxification by transmembrane export across the plasma membrane / antiporter activity / xenobiotic transport / response to osmotic stress / xenobiotic transmembrane transporter activity ...EmrE multidrug transporter complex / amino-acid betaine transmembrane transporter activity / glycine betaine transport / choline transmembrane transporter activity / choline transport / xenobiotic detoxification by transmembrane export across the plasma membrane / antiporter activity / xenobiotic transport / response to osmotic stress / xenobiotic transmembrane transporter activity / transmembrane transporter activity / xenobiotic metabolic process / transmembrane transport / cellular response to xenobiotic stimulus / response to xenobiotic stimulus / DNA damage response / identical protein binding / membrane / plasma membrane 類似検索 - 分子機能 | ||||||
生物種 | ![]() ![]() | ||||||
手法 | 電子線結晶学 / クライオ電子顕微鏡法 / 解像度: 7.5 Å | ||||||
![]() | Fleishman, S.J. / Harrington, S.E. / Enosh, A. / Halperin, D. / Tate, C.G. / Ben-Tal, N. | ||||||
![]() | ![]() タイトル: Quasi-symmetry in the cryo-EM structure of EmrE provides the key to modeling its transmembrane domain. 著者: Sarel J Fleishman / Susan E Harrington / Angela Enosh / Dan Halperin / Christopher G Tate / Nir Ben-Tal / ![]() 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. #1: ![]() タイトル: Three-dimensional structure of the bacterial multidrug transporter EmrE shows it is an asymmetric homodimer. 著者: Iban Ubarretxena-Belandia / Joyce M Baldwin / Shimon Schuldiner / Christopher G Tate / ![]() 要旨: The small multidrug resistance family of transporters is widespread in bacteria and is responsible for bacterial resistance to toxic aromatic cations by proton-linked efflux. We have determined the ...The small multidrug resistance family of transporters is widespread in bacteria and is responsible for bacterial resistance to toxic aromatic cations by proton-linked efflux. We have determined the three-dimensional (3D) structure of the Escherichia coli multidrug transporter EmrE by electron cryomicroscopy of 2D crystals, including data to 7.0 A resolution. The structure of EmrE consists of a bundle of eight transmembrane alpha-helices with one substrate molecule bound near the centre. The substrate binding chamber is formed from six helices and is accessible both from the aqueous phase and laterally from the lipid bilayer. The most remarkable feature of the structure of EmrE is that it is an asymmetric homodimer. The possible arrangement of the two polypeptides in the EmrE dimer is discussed based on the 3D density map. | ||||||
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構造ビューア | 分子: ![]() ![]() |
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-検証レポート
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-関連構造データ
関連構造データ | ![]() 1087M M: このデータのモデリングに利用したマップデータ |
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類似構造データ |
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集合体
登録構造単位 | ![]()
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要素
#1: タンパク質 | 分子量: 15203.710 Da / 分子数: 2 / 由来タイプ: 組換発現 / 由来: (組換発現) ![]() ![]() ![]() ![]() |
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-実験情報
-実験
実験 | 手法: 電子線結晶学 |
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EM実験 | 試料の集合状態: 2D ARRAY / 3次元再構成法: 電子線結晶学 |
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試料調製
構成要素 | 名称: multidrug-resistance antiporter from E. coli EmrE / タイプ: COMPLEX |
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緩衝液 | pH: 7.5 / 詳細: 20 mM Sodium phosphate pH7.5, 100 mM NaCl, 2mM |
試料 | 包埋: NO / シャドウイング: NO / 染色: NO / 凍結: YES |
急速凍結 | 装置: HOMEMADE PLUNGER / 凍結剤: NITROGEN |
-データ収集
実験機器 | ![]() モデル: Tecnai F30 / 画像提供: FEI Company |
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顕微鏡 | モデル: FEI TECNAI F30 / 日付: 2003年1月1日 |
電子銃 | 電子線源: ![]() |
電子レンズ | モード: BRIGHT FIELD / 倍率(公称値): 60000 X / 最大 デフォーカス(公称値): 1600 nm / 最小 デフォーカス(公称値): 200 nm |
撮影 | 電子線照射量: 15 e/Å2 / フィルム・検出器のモデル: KODAK SO-163 FILM |
放射 | プロトコル: SINGLE WAVELENGTH / 単色(M)・ラウエ(L): M / 散乱光タイプ: electron |
放射波長 | 相対比: 1 |
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解析
3次元再構成 | 解像度: 7.5 Å / 解像度の算出法: OTHER 詳細: Canonical alpha-helices were fitted into a cryo-EM structure of EmrE at 6Angstroms in-plane and 16Angstroms vertical resolution. The sequence segments were assigned based on biophysical and ...詳細: Canonical alpha-helices were fitted into a cryo-EM structure of EmrE at 6Angstroms in-plane and 16Angstroms vertical resolution. The sequence segments were assigned based on biophysical and sequence data as elaborated in the principal citation. The orientation of each helix around its principal axis was set using evolutionary conservation, requiring that evolutionarily conserved positions be packed inside the core of the protein, whereas variable residues face the outside. A kink was introduced in helix C to fit a bend in the cryo-EM structure and according to sequence clues (see principal citation). A full description of potential inaccuracies in the model is presented in the principal citation. In brief, these include the following: the vertical positioning of the helices may be wrong by several Angstroms due to the low vertical resolution of the cryo-EM structure; the orientations of the helices around their principal axes may vary by about 20 degrees; the positions of backbone atoms on the terminal turns of each helix may not conform to alpha-helical ideality as assumed in the model structure. 対称性のタイプ: 2D CRYSTAL | ||||||||||||
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精密化ステップ | サイクル: LAST
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