Structure and dynamics of LC8 complexes with KXTOT-motif peptides: Swallow and dynein intermediate chain compete for a common site
Structure and dynamics of LC8 complexes with KXTOT-motif peptides: Swallow and dynein intermediate chain compete for a common site
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DOI：
10.1016/j.jmb.2007.05.046
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发表时间：
2007-08-10
影响因子：
5.6
通讯作者：
Barbar, Elisar
中科院分区：
文献类型：
--
作者：
Benison, Gregory;Karplus, P. Andrew;Barbar, Elisar
动力蛋白轻链LC8是细胞质动力蛋白运动复合物的一个完整亚基，直接结合并促进动力蛋白中间链（IC）的组装。LC8还与多种假定的动力蛋白载物分子相互作用，如Bim，一种促凋亡的Bcl2家族蛋白，具有KXTQT识别序列和神经元一氧化氮合酶（nNOS），具有GIQVD指纹，但在LC8二聚体界面上具有相同的结合凹槽。这里报道的工作调查了LC8与IC和假定的货物Swallow的相互作用，它们共享KXTQT识别序列，并解决了LC8作为动力蛋白的一部分如何介导与货物结合的明显悖论。通过x射线衍射分析，果蝇LC8与IC和Swallow肽结合的结构表明，IC和Swallow肽在二聚体界面上以相同的凹槽结合。通过氢同位素交换实验，利用异核磁共振波谱分析了结合LC8和游离LC8之间的柔韧性差异。肽结合主要在与肽直接相互作用的残基（如在界面上缠绕的β链和螺旋α 2的n端）中增加了对交换的保护。与LC8/nNOS复合物的比较显示了GIQVD和KXTQT指纹是如何在同一凹槽中被识别的。LC8/IC和LC8/Swa的相似结构以及Swallow更紧密的结合使LC8作为货物接头蛋白的作用受到质疑，并表明LC8与Swallow的结合可能具有另一种功能，可能是二聚化引擎，而这种功能独立于其在动力蛋白中的作用。(C) 2007 Elsevier Ltd.版权所有。
The dynein light chain LC8 is an integral subunit of the cytoplasmic dynein motor complex that binds directly to and promotes assembly of the dynein intermediate chain (IC). LC8 interacts also with a variety of putative dynein cargo molecules such as Bim, a proapoptotic Bcl2 family protein, which have the KXTQT recognition sequence and neuronal nitric oxide synthase (nNOS), which has the GIQVD fingerprint but shares the same binding grooves at the LC8 dimer interface. The work reported here investigates the interaction of LC8 with IC and a putative cargo, Swallow, which share the KXTQT recognition sequence, and addresses the apparent paradox of how LC8, as part of dynein, mediates binding to cargo. The structures of Drosophila LC8 bound to peptides from IC and Swallow solved by X-ray diffraction show that the IC and Swallow peptides bind in the same grooves at the dimer interface. Differences in flexibility between bound and free LC8 were evaluated from hydrogen isotope exchange experiments using heteronuclear NMR spectroscopy. Peptide binding causes an increase in protection from exchange primarily in residues that interact directly with the peptide, such as the beta-strand intertwined at the interface and the N-terminal end of helix alpha 2. There is considerably more protection upon Swallow binding, consistent with tighter binding relative to IC. Comparison with the LC8/nNOS complex shows how both the GIQVD and KXTQT fingerprints are recognized in the same groove. The similar structures of LC8/IC and LC8/Swa and the tighter binding of Swallow call into question the role for LC8 as a cargo adaptor protein, and suggest that binding of LC8 to Swallow serves another function, possibly that of a dimerization engine, which is independent of its role in dynein. (C) 2007 Elsevier Ltd. All rights reserved.