1SFE:
reference: Crystal structure of a suicidal DNA repair protein: the Ada O6-methylguanine-DNA methyltransferase from E. coli., Moore MH, Gulbis JM, Dodson EJ, Demple B, Moody PC, EMBO J 1994 Apr 1;13(7):1495-501. PMID: 8156986

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