2CBF:
reference: The X-ray structure of a cobalamin biosynthetic enzyme, cobalt-precorrin-4 methyltransferase., Schubert HL, Wilson KS, Raux E, Woodcock SC, Warren MJ, Nat Struct Biol 1998 Jul;5(7):585-92. PMID: 9665173

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