Mapping the interactions between Lys48 and Lys63-linked di-ubiquitins and a ubiquitin-interacting motif of S5a
Mapping the interactions between Lys48 and Lys63-linked di-ubiquitins and a ubiquitin-interacting motif of S5a
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DOI：
10.1016/j.jmb.2007.02.037
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发表时间：
2007-05-04
影响因子：
5.6
通讯作者：
Fushman, David
中科院分区：
文献类型：
--
作者：
Haririnia, Aydin;D'Onofrio, Mariapina;Fushman, David
许多细胞过程是由（多）泛素介导的信号事件调控的，这些信号事件包括一个泛素或一个泛素分子链通过一个特定的赖氨酸连接的底物蛋白的共价修饰。值得注意的是，多泛素化的结果是连锁依赖的。例如，lys48链是蛋白酶体降解的主要信号，而lys63链则是非蛋白酶体降解信号。尽管在涉及泛素的各种细胞途径的表征方面取得了重大进展，但对下游细胞效应物识别多泛素链的结构细节的了解尚不清楚。本研究利用核磁共振技术研究了蛋白酶体亚基S5a的泛素相互作用基序（UIM）与多泛素链最简单的模型二泛素的相互作用，以深入了解蛋白酶体识别多泛素的机制。我们绘制了结合界面，并表征了UIM与Lys48-和lys63连接的二泛素链结合的化学计量学和过程。我们的数据提供了第一个直接证据，证明UIM结合涉及lys48连接的双泛素的构象转变，从而打开疏水结构域间界面。这使得UIM可以进入界面，并直接结合到与UIM：单泛素复合物中使用的相同的泛素疏水斑块表面。结果表明：最多两个UIM分子可以结合二泛素，并且在lys48和lys63链中，UIM与二泛素中泛素单元的结合界面基本相同。我们的数据提出了UIM和全长S5a与二泛素结合的可能结构模型。(c) 2007 Elsevier Ltd.版权所有。
Numerous cellular processes are regulated by (poly)ubiquitin-mediated signaling events, which involve a covalent modification of the substrate protein by a single ubiquitin or a chain of ubiquitin molecules linked via a specific lysine. Remarkably, the outcome of polyubiquitination is linkage-dependent. For example, Lys48-linked chains are the principal signal for proteasomal degradation, while Lys63-linked chains act as nonproteolytic signals. Despite significant progress in characterization of various cellular pathways involving ubiquitin, understanding of the structural details of polyubiquitin chain recognition by downstream cellular effectors is missing. Here we use NMR to study the interaction of a ubiquitin-interacting motif (UIM) of the proteasomal subunit S5a with di-ubiquitin, the simplest model for polyubiquitin chain, to gain insights into the mechanism of polyubiquitin recognition by the proteasome. We have mapped the binding interface and characterized the stoichiometry and the process of UIM binding to Lys48- and Lys63-linked di-ubiquitin chains. Our data provide the first direct evidence that UIM binding involves a conformational transition in Lys48-linked di-ubiquitin, which opens the hydrophobic interdomain interface. This allows UIM to enter the interface and bind directly to the same ubiquitin hydrophobic-patch surface as utilized in UIM: monoubiquitin complexes. The results indicate that: up to two UIM molecules can bind di-ubiquitin, and the binding interface between UIM and ubiquitin units in di-ubiquitin is essentially the same for both Lys48and Lys63-linked chains. Our data suggest possible structural models for the binding of UIM and of full-length S5a to di-ubiquitin. (c) 2007 Elsevier Ltd. All rights reserved.