Insights into E3 ligase activity revealed by a SUMO-RanGAP1-Ubc9-Nup358 complex
Insights into E3 ligase activity revealed by a SUMO-RanGAP1-Ubc9-Nup358 complex
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DOI：
10.1038/nature03588
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发表时间：
2005-06-02
期刊：
影响因子：
64.8
通讯作者：
Lima, CD
中科院分区：
文献类型：
--
作者：
Reverter, D;Lima, CD
SUMO-1（小泛素相关修饰物）属于泛素（Ub）和泛素样（Ubl）蛋白家族。SUMO结合发生在蛋白质靶标内的特定赖氨酸残基上，通过改变活性或细胞定位或通过保护底物免受泛素化而改变蛋白质功能，从而调节参与分化、凋亡、细胞周期和应激反应的途径（1，2）。Ub/Ubl结合发生在连续步骤中，需要E2结合蛋白和E3连接酶的协同作用（1，2）。除了作为SUMO E3之外，核孔蛋白Nup 358/RanBP 2还通过复合物中的相互作用将SUMO缀合的RanGAP 1定位于核孔复合物的细胞质面，该复合物还包括Ubc 9，SUMO E2缀合蛋白（3-6）。在这里，我们描述了Ubc 9，Nup 358/RanBP 2 E3连接酶结构域（IR 1-M）和SUMO-1共轭的RanGAP 1的羧基末端结构域的四蛋白复合物的3.0埃晶体结构。结合用另外的底物获得的生物化学和动力学数据的结构见解支持这样的模型，其中Nup 358/RanBP 2通过结合SUMO和Ubc 9两者以将SUMO-E2-硫酯定位在最佳方向以增强缀合而充当E3。
SUMO-1 ( for small ubiquitin-related modifier) belongs to the ubiquitin (Ub) and ubiquitin-like (Ubl) protein family. SUMO conjugation occurs on specific lysine residues within protein targets, regulating pathways involved in differentiation, apoptosis, the cell cycle and responses to stress by altering protein function through changes in activity or cellular localization or by protecting substrates from ubiquitination(1,2). Ub/Ubl conjugation occurs in sequential steps and requires the concerted action of E2 conjugating proteins and E3 ligases(1,2). In addition to being a SUMO E3, the nucleoporin Nup358/RanBP2 localizes SUMO-conjugated RanGAP1 to the cytoplasmic face of the nuclear pore complex by means of interactions in a complex that also includes Ubc9, the SUMO E2 conjugating protein(3-6). Here we describe the 3.0-angstrom crystal structure of a four-protein complex of Ubc9, a Nup358/RanBP2 E3 ligase domain ( IR1-M) and SUMO-1 conjugated to the carboxy-terminal domain of RanGAP1. Structural insights, combined with biochemical and kinetic data obtained with additional substrates, support a model in which Nup358/ RanBP2 acts as an E3 by binding both SUMO and Ubc9 to position the SUMO - E2- thioester in an optimal orientation to enhance conjugation.