Department of Biomedicine, University Basel, Hebelstrasse 20, 4031 Basel, Switzerland.
Essays Biochem. 2012;52:37-50. doi: 10.1042/bse0520037.
Ubiquitination, the covalent attachment of the small protein modifier ubiquitin to a substrate protein is involved in virtually all cellular processes by mediating the regulated degradation of proteins. Aside from proteasomal degradation, ubiquitination plays important roles in transcriptional regulation, protein trafficking, including endocytosis and lysosomal targeting, and activation of kinases involved in signalling processes. A three-tiered enzymatic cascade consisting of E1 or ubiquitin-activating enzyme, E2 or ubiquitin-conjugating enzyme, and E3, or ubiquitin ligases, is necessary to achieve the many forms of ubiquitination known to date. In this chapter, we summarize the current knowledge on the enzymatic machinery necessary for ubiquitin activation and ligation, as well as its removal, and provide some insight into the complexity of regulatory processes governed by ubiquitination.
泛素化，即将小蛋白修饰物泛素共价连接到底物蛋白上，通过调节蛋白质的降解，参与几乎所有的细胞过程。除了蛋白酶体降解，泛素化在转录调控、蛋白质运输（包括内吞作用和溶酶体靶向）以及参与信号转导过程的激酶的激活中发挥重要作用。一个由 E1 或泛素激活酶、E2 或泛素结合酶和 E3 或泛素连接酶组成的三级酶级联反应，是实现迄今为止已知的多种泛素化形式所必需的。在本章中，我们总结了泛素激活和连接以及其去除所需的酶机制的最新知识，并深入了解了由泛素化调控的复杂的调节过程。
