UBA1 is located in both the cytoplasm and nucleus (Grenfell et al. 1994). Activation of ubiquitin by UBA1 proceeds through 3 steps: adenylation of ubiquitin, conjugation of ubiquitin from adenyl-ubiquitin to an internal cysteine residue of UBA1, and adenylation of a second molecule of ubiquitin. In the third step, the UBA1-ubiquitin conjugate adenylates the C-terminal glycine of a second ubiquitin molecule. This results in UBA1 loaded with 2 ubiquitin molecules, one of which is conjugated to an internal cysteine residue of UBA1 and one of which is adenylated and non-covalently bound to UBA1 (Jin et al. 2007, inferred from the rabbit homologue in Haas et al. 1982, Hershko et al. 1983, reviewed in Groettrup et al. 2008)
Li, X, Gygi, SP, Jin, J, Harper, JW
Hofmann, K, Pelzer, C, Groettrup, M, Schmidtke, G
Rose, IA, Hershko, A, Haas, AL, Warms, JV
Ciechanover, A, Elias, S, Heller, H, Hershko, A
Schwartz, AL, Ciechanover, A, Grenfell, SJ, Handley-Gearhart, PM, Trausch-Azar, JS
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