3guc is a 2 chain structure with sequence from Homo sapiens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
↑Komatsu M, Chiba T, Tatsumi K, Iemura S, Tanida I, Okazaki N, Ueno T, Kominami E, Natsume T, Tanaka K. A novel protein-conjugating system for Ufm1, a ubiquitin-fold modifier. EMBO J. 2004 May 5;23(9):1977-86. Epub 2004 Apr 8. PMID:15071506 doi:https://dx.doi.org/10.1038/sj.emboj.7600205
↑Zheng M, Gu X, Zheng D, Yang Z, Li F, Zhao J, Xie Y, Ji C, Mao Y. UBE1DC1, an ubiquitin-activating enzyme, activates two different ubiquitin-like proteins. J Cell Biochem. 2008 Aug 15;104(6):2324-34. doi: 10.1002/jcb.21791. PMID:18442052 doi:https://dx.doi.org/10.1002/jcb.21791
↑Bacik JP, Walker JR, Ali M, Schimmer AD, Dhe-Paganon S. Crystal structure of the human ubiquitin-activating enzyme 5 (UBA5) bound to ATP: mechanistic insights into a minimalistic E1 enzyme. J Biol Chem. 2010 Jun 25;285(26):20273-80. Epub 2010 Apr 5. PMID:20368332 doi:10.1074/jbc.M110.102921