1K6W:
reference: The structure of Escherichia coli cytosine deaminase., Ireton GC, McDermott G, Black ME, Stoddard BL, J Mol Biol 2002 Jan 25;315(4):687-97. PMID: 11812140

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