Desterro J M, Thomson J, Hay R T
School of Biomedical Science, University of St. Andrews, Fife, UK.
FEBS Lett. 1997 Nov 17;417(3):297-300. doi: 10.1016/s0014-5793(97)01305-7.
Ubiquitin conjugating enzymes participate in the thioester cascade that leads to protein ubiquitination. Although Ubc9 is homologous to E2 ubiquitin conjugating enzymes we have shown that it is unable to form a thioester with ubiquitin, but can form a thioester with the small ubiquitin-like protein SUMO. Thus Ubc9 is a SUMO conjugating enzyme rather than a ubiquitin conjugating enzyme. Transacetylation of Ubc9 by SUMO is not mediated by the E1 ubiquitin activating enzyme, but by a distinct enzymatic activity. SUMO conjugation to target proteins is mediated by a different, but parallel pathway to ubiquitination.
泛素缀合酶参与导致蛋白质泛素化的硫酯级联反应。尽管Ubc9与E2泛素缀合酶同源，但我们已经表明它无法与泛素形成硫酯，却能与小泛素样蛋白SUMO形成硫酯。因此，Ubc9是一种SUMO缀合酶而非泛素缀合酶。SUMO对Ubc9的转乙酰化不是由E1泛素激活酶介导的，而是由一种独特的酶活性介导。SUMO与靶蛋白的缀合是通过一条与泛素化不同但平行的途径介导的。
