1KPS:
reference: Structural basis for E2-mediated SUMO conjugation revealed by a complex between ubiquitin-conjugating enzyme Ubc9 and RanGAP1., Bernier-Villamor V, Sampson DA, Matunis MJ, Lima CD, Cell 2002 Feb 8;108(3):345-56. PMID: 11853669

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