1D3W:
reference: Atomically defined mechanism for proton transfer to a buried redox centre in a protein., Chen K, Hirst J, Camba R, Bonagura CA, Stout CD, Burgess BK, Armstrong FA, Nature 2000 Jun 15;405(6788):814-7. PMID: 10866206

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