4ISQ:
reference: Crystal Structures of Botulinum Neurotoxin DC in Complex with Its Protein Receptors Synaptotagmin I and II., Berntsson RP, Peng L, Svensson LM, Dong M, Stenmark P, Structure. 2013 Sep 3;21(9):1602-11. doi: 10.1016/j.str.2013.06.026. Epub 2013, Aug 8. PMID: 23932591

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