Structural basis for ubiquitin-mediated dimerization and activation of the ubiquitin protein ligase Cbl-b
Structural basis for ubiquitin-mediated dimerization and activation of the ubiquitin protein ligase Cbl-b
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DOI：
10.1016/j.molcel.2007.06.023
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发表时间：
2007-08-03
期刊：
影响因子：
16
通讯作者：
Gehring, Kalle
中科院分区：
文献类型：
--
作者：
Peschard, Pascal;Kozlov, Guennadi;Gehring, Kalle
Cbl蛋白是E3泛素连接酶，其是许多受体酪氨酸激酶的负调节剂。Cbl-b和c-Cbl含有一个泛素相关（乌巴）结构域，它存在于多种参与泛素介导过程的蛋白质中。尽管具有高度的序列同一性，但Cbl乌巴结构域显示出显著不同的泛素结合特性。在这里，我们报告的晶体结构的乌巴结构域的Cbl-b在复杂的泛素在1.9埃分辨率。结构揭示了一种非典型的机制，泛素识别的第一螺旋的乌巴。乌巴结构域的螺旋2和3形成第二结合表面，其介导晶体和溶液中的IJIBA二聚化。定点突变表明，Cbl-b二聚化是由泛素结合调节的，并且是Cbl-b酪氨酸磷酸化和Cbl-b底物泛素化所必需的。这些研究证明了泛素通过促进蛋白质二聚化在调节生物活性中的作用。
Cbl proteins are E3 ubiquitin ligases that are negative regulators of many receptor tyrosine kinases. Cbl-b and c-Cbl contain a ubiquitinassociated (UBA) domain, which is present in a variety of proteins involved in ubiquitinmediated processes. Despite high sequence identity, Cbl UBA domains display remarkably different ubiquitin-binding properties. Here, we report the crystal structure of the UBA domain of Cbl-b in complex with ubiquitin at 1.9 angstrom resolution. The structure reveals an atypical mechanism of ubiquitin recognition by the first helix of the UBA. Helices 2 and 3 of the UBA domain form a second binding surface, which mediates IJIBA dimerization in the crystal and in solution. Site-directed mutagenesis demonstrates that Cbl-b dimerization is regulated by ubiquitin binding and required for tyrosine phosphorylation of Cbl-b and ubiquitination of Cbl-b substrates. These studies demonstrate a role for ubiquitin in regulating biological activity by promoting protein dimerization.