1GCA:
reference: The 1.7 A refined X-ray structure of the periplasmic glucose/galactose receptor from Salmonella typhimurium., Zou JY, Flocco MM, Mowbray SL, J Mol Biol 1993 Oct 20;233(4):739-52. PMID: 8240551

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