1BTL:
reference: Crystal structure of Escherichia coli TEM1 beta-lactamase at 1.8 A resolution., Jelsch C, Mourey L, Masson JM, Samama JP, Proteins 1993 Aug;16(4):364-83. PMID: 8356032

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