3CPA:
reference: X-ray crystallographic investigation of substrate binding to carboxypeptidase A at subzero temperature., Christianson DW, Lipscomb WN, Proc Natl Acad Sci U S A. 1986 Oct;83(20):7568-72. PMID: 3463986

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