1RIB:
reference: Structure and function of the Escherichia coli ribonucleotide reductase protein R2., Nordlund P, Eklund H, J Mol Biol 1993 Jul 5;232(1):123-64. PMID: 8331655

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