5X9R

Structural insights into the elevator-like mechanism of the sodium/citrate symporter CitS

Summary for 5X9R

• Entry DOI: 10.2210/pdb5x9r/pdb
• Related: 5XAR 5XAS 5XAT
• Descriptor: Citrate-sodium symporter, CITRATE ANION, beta-D-glucopyranose (3 entities in total)
• Functional Keywords: cits, citrate transporter, sodium/citrate symporter, 2-hct, transport protein
• Biological source: Klebsiella pneumoniae
• Cellular location: Cell membrane; Multi-pass membrane protein: P31602
• Total number of polymer chains: 2
• Total formula weight: 94085.37

Authors

Jin, M.S.,Kim, J.W.,Kim, S.,Kim, S.,Lee, H.,Lee, J.-O. (deposition date: 2017-03-08, release date: 2017-06-14, Last modification date: 2023-11-22)

Primary citation

Kim, J.W.,Kim, S.,Kim, S.,Lee, H.,Lee, J.O.,Jin, M.S.
Structural insights into the elevator-like mechanism of the sodium/citrate symporter CitS
Sci Rep, 7:2548-2548, 2017

PubMed Abstract: The sodium-dependent citrate transporter of Klebsiella pneumoniae (KpCitS) belongs to the 2-hydroxycarboxylate transporter (2-HCT) family and allows the cell to use citrate as sole carbon and energy source in anaerobic conditions. Here we present crystal structures of KpCitS in citrate-bound outward-facing, citrate-bound asymmetric, and citrate-free inward-facing state. The structures reveal that the KpCitS dimerization domain remains stationary throughout the transport cycle due to a hydrogen bond network as well as extensive hydrophobic interactions. In contrast, its transport domain undergoes a ~35° rigid-body rotation and a ~17 Å translocation perpendicular to the membrane to expose the substrate-binding site alternately to either side of the membrane. Furthermore, homology models of two other 2-HCT proteins based on the KpCitS structure offer structural insights into their differences in substrate specificity at a molecular level. On the basis of our results and previous biochemical data, we propose that the activity of the 2-HCT CitS involves an elevator-like movement in which the transport domain itself traverses the lipid bilayer, carrying the substrate into the cell in a sodium-dependent manner.

PubMed: 28566738
DOI: 10.1038/s41598-017-02794-x

Experimental method

X-RAY DIFFRACTION (3.98 Å)