1SS9:
reference: Intermediate trapping on a mutant retaining alpha-galactosyltransferase identifies an unexpected aspartate residue., Lairson LL, Chiu CP, Ly HD, He S, Wakarchuk WW, Strynadka NC, Withers SG, J Biol Chem 2004 Jul 2;279(27):28339-44. Epub 2004 Apr 9. PMID: 15075344

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