4AL3:
reference: A FRET Enzyme-Based Probe for Monitoring Hydrogen Sulfide., Strianese M, Palm GJ, Milione S, Kuhl O, Hinrichs W, Pellecchia C, Inorg Chem. 2012 Oct 16. PMID: 23072298

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