2AAK:
reference: Three-dimensional structure of a ubiquitin-conjugating enzyme (E2)., Cook WJ, Jeffrey LC, Sullivan ML, Vierstra RD, J Biol Chem 1992 Jul 25;267(21):15116-21. PMID: 1321826

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