An expanded conformation of single-ring GroEL-GroES complex encapsulates an 86 kDa substrate
An expanded conformation of single-ring GroEL-GroES complex encapsulates an 86 kDa substrate
复制标题
DOI：
10.1016/j.str.2006.09.010
复制
发表时间：
2006-11-01
期刊：
影响因子：
5.7
通讯作者：
Ludtke, Steven J.
中科院分区：
文献类型：
--
作者：
Chen, Dong-Hua;Song, Jiu-Li;Ludtke, Steven J.
电子低温显微镜揭示了一个前所未有的构象的GroEL（SR 398）结合GroES在Mg-ATP的存在下的单环突变体。这种构象表现出折叠腔的相当大的膨胀，其体积比GroEL-GroES-（ADP）（7）复合物中的等效顺式腔的X射线结构大80%。这种扩展的构象可以包封线粒体支链α-酮酸脱氢酶的86 kDa异二聚体（α β）组装中间体，这是迄今为止观察到的顺式包封的最大底物。发现SR 398-GroES-Mg-ATP复合物作为标准构象和扩展构象的混合物存在，而不管底物的存在或不存在。然而，即使是一个小的基板的存在下，导致一个显着的偏向扩展构象。一系列电子冷冻显微镜研究以及保护底物的α和β亚基免受胰蛋白酶消化支持大组装中间体的封装。
Electron cryomicroscopy reveals an unprecedented conformation of the single-ring mutant of GroEL (SR398) bound to GroES in the presence of Mg-ATP. This conformation exhibits a considerable expansion of the folding cavity, with similar to 80% more volume than the X-ray structure of the equivalent cis cavity in the GroEL-GroES-(ADP)(7) complex. This expanded conformation can encapsulate an 86 kDa heterodimeric (alpha beta) assembly intermediate of mitochondrial branched-chain alpha-ketoacid dehydrogenase, the largest substrate ever observed to be cis encapsulated. The SR398-GroES-Mg-ATP complex is found to exist as a mixture of standard and expanded conformations, regardless of the absence or presence of the substrate. However, the presence of even a small substrate causes a pronounced bias toward the expanded conformation. Encapsulation of the large assembly intermediate is supported by a series of electron cryomicroscopy studies as well as the protection of both alpha and beta subunits of the substrate from tryptic digestion.