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Title | Structure and substrate-induced conformational changes of the secondary citrate/sodium symporter CitS revealed by electron crystallography. |
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Journal, issue, pages | Structure, Vol. 21, Issue 7, Page 1243-1250, Year 2013 |
Publish date | Jul 2, 2013 |
Authors | Fabian Kebbel / Mareike Kurz / Marcel Arheit / Markus G Grütter / Henning Stahlberg / |
PubMed Abstract | 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’’. |
External links | Structure / PubMed:23810698 |
Methods | EM (electron crystallography) |
Resolution | 6.0 Å |
Structure data | EMDB-2387: Structure and substrate induced conformational changes of the secondary citrate/sodium symporter CitS revealed by electron crystallography |
Source |
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Keywords | TRANSPORT PROTEIN / SECONDARY TRANSPORTER / MEMBRANE PROTEIN |