1Y21:
reference: Heme-assisted S-nitrosation of a proximal thiolate in a nitric oxide transport protein., Weichsel A, Maes EM, Andersen JF, Valenzuela JG, Shokhireva TKh, Walker FA, Montfort WR, Proc Natl Acad Sci U S A. 2005 Jan 18;102(3):594-9. Epub 2005 Jan 6. PMID: 15637157

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