5A1S:
reference: Mechanism of Na(+)-dependent citrate transport from the structure of an asymmetrical CitS dimer., Wohlert D, Grotzinger MJ, Kuhlbrandt W, Yildiz O, Elife. 2015 Dec 4;4. pii: e09375. doi: 10.7554/eLife.09375. PMID: 26636752

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).