3SDP:
reference: The 2.1-A resolution structure of iron superoxide dismutase from Pseudomonas ovalis., Stoddard BL, Howell PL, Ringe D, Petsko GA, Biochemistry 1990 Sep 25;29(38):8885-93. PMID: 2271564

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