1SG9:
reference: A novel mode of dimerization via formation of a glutamate anhydride crosslink in a protein crystal structure., Agarwal R, Burley SK, Swaminathan S, Proteins. 2008 May 1;71(2):1038-41. PMID: 18247349

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