4ZYR:
reference: Structure of LacY with an alpha-substituted galactoside: Connecting the binding site to the protonation site., Kumar H, Finer-Moore JS, Kaback HR, Stroud RM, Proc Natl Acad Sci U S A. 2015 Jul 21;112(29):9004-9. doi:, 10.1073/pnas.1509854112. Epub 2015 Jul 8. PMID: 26157133

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