1G4V:
reference: Strain is more important than electrostatic interaction in controlling the pKa of the catalytic group in aspartate aminotransferase., Mizuguchi H, Hayashi H, Okada K, Miyahara I, Hirotsu K, Kagamiyama H, Biochemistry 2001 Jan 16;40(2):353-60. PMID: 11148029

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