Vuillard L, Nicholson J, Hay R T
School of Biomedical Science, University of St. Andrews, Fife, UK.
FEBS Lett. 1999 Jul 23;455(3):311-4. doi: 10.1016/s0014-5793(99)00895-9.
Activation of transcription factor NF-kappaB is accomplished by degradation of its inhibitor IkappaBalpha. Signal induced phosphorylation of IkappaBalpha on serine 32 and 36 targets the protein for ubiquitination on lysine 21 and 22. Here we use a phosphorylated peptide substrate representing residues 20-43 of IkappaBalpha to investigate requirements for ubiquitination of IkappaBalpha. Phosphorylation dependent polyubiquitination is carried out by a multiprotein complex containing betaTrCP, Skp1 and Cdc53 (Cull). In the presence of ubiquitin activating enzyme and the protein complex containing betaTrCP, polyubiquitination of IkappaBalpha peptide was dependent on the presence of Cdc34, while Ubc5 only stimulated mono- and di-ubiquitination.
转录因子NF-κB的激活是通过其抑制剂IκBα的降解来实现的。信号诱导IκBα在丝氨酸32和36位点的磷酸化，使该蛋白在赖氨酸21和22位点被泛素化。在这里，我们使用一个代表IκBα 20 - 43位残基的磷酸化肽底物来研究IκBα泛素化的条件。磷酸化依赖性多聚泛素化由包含βTrCP、Skp1和Cdc53（Cull）的多蛋白复合物进行。在存在泛素激活酶和包含βTrCP的蛋白复合物的情况下，IκBα肽的多聚泛素化依赖于Cdc34的存在，而Ubc5仅刺激单泛素化和双泛素化。
