The 'sequential allosteric ring' mechanism in the eukaryotic chaperonin-assisted folding of actin and tubulin
The 'sequential allosteric ring' mechanism in the eukaryotic chaperonin-assisted folding of actin and tubulin
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DOI：
10.1093/emboj/20.15.4065
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发表时间：
2001-08-01
期刊：
影响因子：
11.4
通讯作者：
Valpuesta, JM
中科院分区：
文献类型：
--
作者：
Llorca, O;Martín-Benito, J;Valpuesta, JM
真核细胞质中肌动蛋白和微管蛋白的折叠完成需要它们与胞质伴侣蛋白CCT [含无尾复合多肽1（TCP-1）的伴侣蛋白]相互作用。无核苷酸的CCT与肌动蛋白或微管蛋白复合的三维重建表明，CCT通过亚基特异性和几何形状依赖性的相互作用使细胞骨架蛋白稳定在开放和准折叠构象中。在此，我们发现，在ATP结合时，通过不可水解的类似物AMP-PNP（5 ' -腺苷酰亚胺-二磷酸）模拟，与CCT-α-肌动蛋白和CCT-β-微管蛋白复合物两者结合，伴侣蛋白组分经历顶端结构域的协同运动，导致腔被八个顶端结构域的螺旋突起封闭。然而，与GroE系统相反，这种封闭状态的产生不会诱导底物释放到伴侣蛋白腔中，并且两种细胞骨架蛋白都保持与伴侣蛋白顶端结构域结合。α-肌动蛋白和β-微管蛋白的AMP-PNP-CCT结合构象与它们各自的天然原子结构的对接表明这两种蛋白质都向它们的天然状态发展。
Folding to completion of actin and tubulin in the eukaryotic cytosol requires their interaction with cytosolic chaperonin CCT [chaperonin containing tailless complex polypeptide 1 (TCP-1)]. Three-dimensional reconstructions of nucleotide-free CCT complexed to either actin or tubulin show that CCT stabilizes both cytoskeletal proteins in open and quasi-folded conformations mediated through interactions that are both subunit specific and geometry dependent. Here we find that upon ATP binding, mimicked by the non-hydrolysable analog AMP-PNP (5 ' -adenylylimido-diphosphate), to both CCT-alpha -actin and CCT-beta -tubulin complexes, the chaperonin component undergoes concerted movements of the apical domains, resulting in the cavity being closed off by the helical protrusions of the eight apical domains. However, in contrast to the GroE system, generation of this closed state does not induce the release of the substrate into the chaperonin cavity, and both cytoskeletal proteins remain bound to the chaperonin apical domains. Docking of the AMP-PNP-CCT-bound conformations of a-actin and P-tubulin to their respective native atomic structures suggests that both proteins have progressed towards their native states.