2SBT:
reference: A comparison of the three-dimensional structures of subtilisin BPN' and subtilisin novo., Drenth J, Hol WG, Jansonius JN, Koekoek R, Cold Spring Harb Symp Quant Biol 1972;36:107-16. PMID: 4508127

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