Structural insights into the mechanism and E2 specificity of the RBR E3 ubiquitin ligase HHARI.
Structural insights into the mechanism and E2 specificity of the RBR E3 ubiquitin ligase HHARI.
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对 RBR E3 泛素连接酶 HHARI 的机制和 E2 特异性的结构见解。
DOI：
10.1038/s41467-017-00272-6
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发表时间：
2017
影响因子：
16.6
通讯作者：
Olsen,ShaunK
中科院分区：
文献类型：
--
作者：
Yuan,Lingmin;Lv,Zongyang;Atkison,JamesH;Olsen,ShaunK
环间环（RBR）泛素（Ub）E3连接酶通过RING/HECT杂合机制与Ub E2起作用以将Ub缀合至靶蛋白。在这里，我们报告的晶体结构的RBR E3，HHAR 1，在复杂的UbcH 7 ~ Ub硫酯模拟物，揭示了这种同源E2/RBR E3对的特异性的分子基础。该结构还揭示了HHARI的RING 1和UBA样结构域中伴随UbcH 7 ~ Ub结合的重要构象变化，并提供了HHARI以“开放”构象募集E2 ~ Ub的分子基础。除了仅进行转巯基化的E2的最佳功能之外，我们的数据表明HHARI通过以下方式防止Ub从E2到赖氨酸残基的假放电：（1）包含阻止E2 ~ Ub采用“闭合”构象的结构元件和（2）参与促进开放E2 ~ Ub构象的泛素接触。
RING-in-between-RING (RBR) ubiquitin (Ub) E3 ligases function with Ub E2s through a RING/HECT hybrid mechanism to conjugate Ub to target proteins. Here, we report the crystal structure of the RBR E3, HHARI, in complex with a UbcH7 ~ Ub thioester mimetic which reveals the molecular basis for the specificity of this cognate E2/RBR E3 pair. The structure also reveals mechanistically important conformational changes in the RING1 and UBA-like domains of HHARI that accompany UbcH7 ~ Ub binding and provides a molecular basis by which HHARI recruits E2 ~ Ub in an ‘open’ conformation. In addition to optimally functioning with an E2 that solely performs transthiolation, our data suggests that HHARI prevents spurious discharge of Ub from E2 to lysine residues by: (1) harboring structural elements that block E2 ~ Ub from adopting a ‘closed’ conformation and (2) participating in contacts to ubiquitin that promote an open E2 ~ Ub conformation.