ジャーナル: Structure / 年: 2013 タイトル: Structure and substrate-induced conformational changes of the secondary citrate/sodium symporter CitS revealed by electron crystallography. 著者: Fabian Kebbel / Mareike Kurz / Marcel Arheit / Markus G Grütter / Henning Stahlberg / 要旨: The secondary Na+/citrate symporter CitS of Klebsiella pneumoniae is the best-characterized member of the 2-hydroxycarboxylate transporter family. The recent projection structure gave insight into ...The secondary Na+/citrate symporter CitS of Klebsiella pneumoniae is the best-characterized member of the 2-hydroxycarboxylate transporter family. The recent projection structure gave insight into its overall structural organization. Here, we present the three-dimensional map of dimeric CitS obtained with electron crystallography. Each monomer has 13 a-helical transmembrane segments; six are organized in a distal helix cluster and seven in the central dimer interface domain. Based on structural analyses and comparison to VcINDY, we propose a molecular model for CitS, assign the helices, and demonstrate the internal structural symmetry. We also present projections of CitS in several conformational states induced by the presence and absence of sodium and citrate as substrates. Citrate binding induces a defined movement of a helices within the distal helical cluster. Based on this, we propose a substrate translocation site and conformational changes that are in agreement with the transport model of ‘‘alternating access’’.
THE SAMPLE SEQUENCE HAS UNIPROT ACCESSION B5Y216. BUT THE REGISTER OF THE RESIDUES ON THE EM VOLUME ...THE SAMPLE SEQUENCE HAS UNIPROT ACCESSION B5Y216. BUT THE REGISTER OF THE RESIDUES ON THE EM VOLUME MAP IS UNKNOWN, HENCE THE MODEL IS BUILT IN AS A POLY-ALA MODEL. THE COORDINATES REPRESENTS THE TRANSMEMBRANE HELICES OF THE CITRATE:SODIUM SYMPORTER
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実験情報
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実験
実験
手法: 電子線結晶学 / 使用した結晶の数: 79
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: secondary citrate-sodium symporter CitS / タイプ: COMPLEX