2KNM:
reference: The conserved glu in the cyclotide cycloviolacin O2 has a key structural role., Goransson U, Herrmann A, Burman R, Haugaard-Jonsson LM, Rosengren KJ, Chembiochem. 2009 Sep 21;10(14):2354-60. PMID: 19735083

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