5MDL:
reference: Tracking the route of molecular oxygen in O2-tolerant membrane-bound [NiFe] hydrogenase., Kalms J, Schmidt A, Frielingsdorf S, Utesch T, Gotthard G, von Stetten D, van der Linden P, Royant A, Mroginski MA, Carpentier P, Lenz O, Scheerer P, Proc Natl Acad Sci U S A. 2018 Mar 6;115(10):E2229-E2237. doi:, 10.1073/pnas.1712267115. Epub 2018 Feb 20. PMID: 29463722

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