4PFT:
reference: Duplication of genes in an ATP binding cassette transport system increases dynamic range while maintaining ligand specificity., Ghimire-Rijal S, Lu X, Myles DA, Cuneo MJ, J Biol Chem. 2014 Sep 10. pii: jbc.M114.590992. PMID: 25210043

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