LOCATION OF A FOLDING PROTEIN AND SHAPE CHANGES IN GROEL-GROES COMPLEXES IMAGED BY CRYOELECTRON MICROSCOPY
LOCATION OF A FOLDING PROTEIN AND SHAPE CHANGES IN GROEL-GROES COMPLEXES IMAGED BY CRYOELECTRON MICROSCOPY
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DOI：
10.1038/371261a0
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发表时间：
1994-09-15
期刊：
影响因子：
64.8
通讯作者：
SAIBIL, HR
中科院分区：
文献类型：
--
作者：
CHEN, S;ROSEMAN, AM;SAIBIL, HR
由分子伴侣GroEL介导的蛋白质折叠通过其与非天然多肽底物的结合发生，并由ATP水解驱动（1）。这两个过程都受到辅蛋白GroES可逆结合的影响（参考文献2-4）。GroEL和其他伴侣蛋白60分子（5）是由亚基的两个堆叠的七聚体环（6，7）组成的大的圆柱形寡聚体;每个环形成被认为在中心腔（8-10）中结合多肽的笼状结构（8）。伴侣蛋白通过结合或螯合折叠蛋白以防止其聚集而在折叠中起被动作用（11-13），但它们也可以主动解折叠以错误折叠形式捕获的底物蛋白，使其能够呈现生产性折叠构象（14-16）。生物化学研究表明，GroES提高了GroEL功能的效率（2，3，17），但其结构基础尚不清楚。在这里，我们报告的第一个直接可视化，冷冻电子显微镜，非天然蛋白质底物（苹果酸脱氢酶）绑定到移动的，在GroEL的一端的外部域。在ATP存在下向GroEL中添加GroES引起约60度的显著铰链打开。GroES与GroEL外结构域的等效表面结合，但在GroEL寡聚体的与蛋白质底物相对的末端上。
PROTEIN folding mediated by the molecular chaperone GroEL occurs by its binding to non-native polypeptide substrates and is driven by ATP hydrolysis(1). Both of these processes are influenced by the reversible association of the co-protein, GroES (refs 2-4). GroEL and other chaperonin 60 molecules(5) are large, cylindrical oligomers consisting of two stacked heptameric rings of subunits(6,7); each ring forms a cage-like structure(8) thought to bind polypeptides in a central cavity(8-10). Chaperonins play a passive role in folding by binding or sequestering folding proteins to prevent their aggregation(11-13), but they may also actively unfold substrate proteins trapped in misfolded forms, enabling them to assume productive folding conformations(14-16). Biochemical studies show that GroES improves the efficiency of GroEL function(2,3,17), but the structural basis for this is unknown. Here we report the first direct visualization, by cryo-electron microscopy, of a non-native protein substrate (malate dehydrogenase) bound to the mobile, outer domains at one end of GroEL. Addition of GroES to GroEL in the presence of ATP causes a dramatic hinge opening of about 60 degrees. GroES binds to the equivalent surface of the GroEL outer domains, but on the opposite end of the GroEL oligomer to the protein substrate.