4WEP:
reference: YehZYXW of Escherichia coli Is a Low-Affinity, Non-Osmoregulatory Betaine-Specific ABC Transporter., Lang S, Cressatti M, Mendoza KE, Coumoundouros CN, Plater SM, Culham DE, Kimber MS, Wood JM, Biochemistry. 2015 Sep 22;54(37):5735-47. doi: 10.1021/acs.biochem.5b00274. Epub , 2015 Sep 9. PMID: 26325238

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