1BRA:
reference: Relocating a negative charge in the binding pocket of trypsin., Perona JJ, Tsu CA, McGrath ME, Craik CS, Fletterick RJ, J Mol Biol 1993 Apr 5;230(3):934-49. PMID: 8478942

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