4XDI:
reference: Structure of Chlamydomonas reinhardtii THB1, a group 1 truncated hemoglobin with a rare histidine-lysine heme ligation., Rice SL, Boucher LE, Schlessman JL, Preimesberger MR, Bosch J, Lecomte JT, Acta Crystallogr F Struct Biol Commun. 2015 Jun 1;71(Pt 6):718-25. doi:, 10.1107/S2053230X15006949. Epub 2015 May 20. PMID: 26057801

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