Structure of an auxilin-bound clathrin coat and its implications for the mechanism of uncoating
Structure of an auxilin-bound clathrin coat and its implications for the mechanism of uncoating
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DOI：
10.1038/nature03078
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发表时间：
2004-12-02
期刊：
影响因子：
64.8
通讯作者：
Kirchhausen, T
中科院分区：
文献类型：
--
作者：
Fotin, A;Cheng, YF;Kirchhausen, T
网格蛋白包被的小凹从特定的膜隔室内陷并夹断为包被的囊泡。一旦释放，这些囊泡就会迅速脱膜。Hsc 70分子伴侣影响去包被反应，并被含J结构域的辅助伴侣分子生长素引导至网格蛋白晶格上的适当位置（1-4）。这就提出了一个问题，如Hsc 70的ATP水解等局部事件如何催化全局分解。在这里，我们已经使用电子低温显微镜，以确定12埃的分辨率结构，在体外组装的网格蛋白外套与生长素的羧基末端片段，包含网格蛋白结合区域和J域。我们通过计算这些结构和缺乏生长素的结构之间的差异来定位生长素片段（在随附的论文中描述（5））。在向内突出的C-末端螺旋三脚架和两个“踝”节段的交叉之间的接触附近的网格蛋白晶格内，它还接触另一个网格蛋白“腿”的末端结构域。因此，它将Hsc 70招募到一系列关键相互作用的邻近区域。白蛋白结合产生重链接触的局部变化，产生可检测的网格蛋白外壳的全局变形。我们提出了一种机制，通过这种机制，局部不稳定的晶格促进一般的脱膜。
Clathrin-coated pits invaginate from specific membrane compartments and pinch off as coated vesicles. These vesicles then uncoat rapidly once released. The Hsc70 molecular chaperone effects the uncoating reaction, and is guided to appropriate locations on clathrin lattices by the J-domain-containing co-chaperone molecule auxilin(1-4). This raises the question of how a local event such as ATP hydrolysis by Hsc70 can catalyse a global disassembly. Here, we have used electron cryomicroscopy to determine 12-Angstrom-resolution structures of in-vitro-assembled clathrin coats in association with a carboxy-terminal fragment of auxilin that contains both the clathrin-binding region and the J domain. We have located the auxilin fragment by computing differences between these structures and those lacking auxilin (described in an accompanying paper(5)). Auxilin binds within the clathrin lattice near contacts between an inward-projecting C-terminal helical tripod and the crossing of two 'ankle' segments; it also contacts the terminal domain of yet another clathrin 'leg'. It therefore recruits Hsc70 to the neighbourhood of a set of critical interactions. Auxilin binding produces a local change in heavy-chain contacts, creating a detectable global distortion of the clathrin coat. We propose a mechanism by which local destabilization of the lattice promotes general uncoating.