2QXF:
reference: Structure of Escherichia coli exonuclease I in complex with thymidine 5'-monophosphate., Busam RD, Acta Crystallogr D Biol Crystallogr. 2008 Feb;64(Pt 2):206-10. Epub 2008, Jan 16. PMID: 18219121

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