1R4M:
reference: The structure of the APPBP1-UBA3-NEDD8-ATP complex reveals the basis for selective ubiquitin-like protein activation by an E1., Walden H, Podgorski MS, Huang DT, Miller DW, Howard RJ, Minor DL Jr, Holton JM, Schulman BA, Mol Cell 2003 Dec;12(6):1427-37. PMID: 14690597

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