2JYP:
reference: Identification and Structural Characterization of an Unusual RING-Like Sequence within an Extracellular Biomineralization Protein, AP7., Collino S, Kim IW, Evans JS, Biochemistry. 2008 Mar 25;47(12):3745-55. Epub 2008 Feb 26. PMID: 18298090

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