Crystallography and Institute of Structural and Molecular Biology, Birkbeck College London, Malet Street, London, WC1E 7HX, UK.
Department of Genetics, Yale University School of Medicine, Boyer Center, 295 Congress Avenue, New Haven, CT 06510, USA.
Int J Biol Macromol. 2018 Oct 15;118(Pt A):671-675. doi: 10.1016/j.ijbiomac.2018.06.120. Epub 2018 Jun 27.
The chaperonins (GroEL and GroES in Escherichia coli) are ubiquitous molecular chaperones that assist a subset of essential substrate proteins to undergo productive folding to the native state. Using single particle cryo EM and image processing we have examined complexes of E. coli GroEL with the stringently GroE-dependent substrate enzyme RuBisCO from Rhodospirillum rubrum. Here we present snapshots of non-native RuBisCO - GroEL complexes. We observe two distinct substrate densities in the binary complex reminiscent of the two-domain structure of the RuBisCO subunit, so that this may represent a captured form of an early folding intermediate. The occupancy of the complex is consistent with the negative cooperativity of GroEL with respect to substrate binding, in accordance with earlier mass spectroscopy studies.
伴侣蛋白（大肠杆菌中的 GroEL 和 GroES）是普遍存在的分子伴侣，它们协助一部分必需的底物蛋白进行有产性折叠，形成天然状态。使用单颗粒冷冻电镜和图像处理，我们研究了大肠杆菌 GroEL 与严格依赖 GroE 的底物酶 Rhodospirillum rubrum 中的 RuBisCO 的复合物。在这里，我们展示了非天然 RuBisCO-GroEL 复合物的快照。我们在二元复合物中观察到两种不同的底物密度，类似于 RuBisCO 亚基的两个结构域结构，因此这可能代表了一种早期折叠中间体的捕获形式。复合物的占有率与 GroEL 对底物结合的负协同性一致，这与早期的质谱研究结果一致。
