4R1R:
reference: Binding of allosteric effectors to ribonucleotide reductase protein R1: reduction of active-site cysteines promotes substrate binding., Eriksson M, Uhlin U, Ramaswamy S, Ekberg M, Regnstrom K, Sjoberg BM, Eklund H, Structure 1997 Aug 15;5(8):1077-92. PMID: 9309223

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