3WHI:
reference: Formation of the High-Affinity Calcium Binding Site in Pro-subtilisin E with the Insertion Sequence IS1 of Pro-Tk-subtilisin., Uehara R, Angkawidjaja C, Koga Y, Kanaya S, Biochemistry. 2013 Dec 17;52(50):9080-8. doi: 10.1021/bi401342k. Epub 2013 Dec 4. PMID: 24279884

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