Affinity makes the difference: Nonselective interaction of the UBA domain of ubiquilin-1 with monomeric ubiquitin and polyubiquitin chains
Affinity makes the difference: Nonselective interaction of the UBA domain of ubiquilin-1 with monomeric ubiquitin and polyubiquitin chains
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DOI：
10.1016/j.jmb.2007.12.029
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发表时间：
2008-03-14
影响因子：
5.6
通讯作者：
Fushman, David
中科院分区：
文献类型：
--
作者：
Zhang, Daoning;Raasi, Shahri;Fushman, David
Ubiquilin/PLIC蛋白属于UBL-UBA蛋白家族，涉及细胞蛋白的泛素依赖性蛋白酶体降解的调节。人早老素相互作用蛋白ubiquilin-1被认为是治疗亨廷顿病的潜在靶点。泛素与单泛素和多泛素的相互作用是由其乌巴结构域介导的，该结构域是已知的泛素结合结构域中最紧密的泛素结合剂之一。在这里，我们报告的三维结构的乌巴域的泛素-1（UQ 1-乌巴）在溶液中的自由和复合物与泛素。UQ 1-乌巴形成结构上类似于其它已知UBA的紧密的三螺旋束，并以20 μ M的Kd结合于泛素上的疏水片。为了获得对UQ 1-乌巴与多聚泛素链的相互作用的结构见解，我们绘制了UQ 1-乌巴与Lys 48-和Lys 63-连接的双泛素之间的结合界面，并表征了UQ 1-乌巴与这些链结合的强度。我们的NMR数据显示，UQ 1-乌巴与两条链中的单个泛素单元以类似于其与单泛素的相互作用的模式相互作用，尽管具有改善的链结合亲和力。我们的结果表明，与hHR 23 A的UBA 2对Lys 48连接的链具有强结合偏好相反，UQ 1-乌巴对特定链连接或同一链中两个泛素部分之间的结合选择性很小或没有。在这项研究中获得的结构数据提供了见解的多样性的多聚泛素链识别的乌巴结构域的可能的结构原因。(c)2007爱思唯尔有限公司版权所有。
Ubiquilin/PLIC proteins belong to the family of UBL-UBA proteins implicated in the regulation of the ubiquitin-dependent proteasomal degradation of cellular proteins. A human presenilin-interacting protein, ubiquilin-1, has been suggested as potential therapeutic target for treating Huntington's disease. Ubiquilin's interactions with mono- and polyubiquitins are mediated by its UBA domain, which is one of the tightest ubiquitin binders among known ubiquitin-binding domains. Here we report the three-dimensional structure of the UBA domain of ubiquilin-1 (UQ1-UBA) free in solution and in complex with ubiquitin. UQ1-UBA forms a compact three-helix bundle structurally similar to other known UBAs, and binds to the hydrophobic patch on ubiquitin with a K-d of 20 mu M. To gain structural insights into UQ1-UBA's interactions with polyubiquitin chains, we have mapped the binding interface between UQ1-UBA and Lys48- and Lys63-linked di-ubiquitins and characterized the strength of UQ1-UBA binding to these chains. Our NMR data show that UQ1-UBA interacts with the individual ubiquitin units in both chains in a mode similar to its interaction with mono-ubiquitin, although with an improved binding affinity for the chains. Our results indicate that, in contrast to UBA2 of hHR23A that has strong binding preference for Lys48-linked chains, UQ1-UBA shows little or no binding selectivity toward a particular chain linkage or between the two ubiquitin moieties in the same chain. The structural data obtained in this study provide insights into the possible structural reasons for the diversity of polyubiquitin chain recognition by UBA domains. (c) 2007 Elsevier Ltd. All rights reserved.