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首页> 外文期刊>Journal of Molecular Biology >Structural changes in GroEL effected by binding a denatured protein substrate.
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Structural changes in GroEL effected by binding a denatured protein substrate.

机译：GroEL的结构变化通过结合变性的蛋白质底物而实现。

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摘要

In the absence of nucleotides or cofactors, the Escherichia coli chaperonin GroEL binds select proteins in non-native conformations, such as denatured glutamine synthetase (GS) monomers, preventing their aggregation and spontaneous renaturation. The nature of the GroEL-GS complexes thus formed, specifically the effect on the conformation of the GroEL tetradecamer, has been examined by electron microscopy. We find that specimens of GroEL-GS are visibly heterogeneous, due to incomplete loading of GroEL with GS. Images contain particles indistinguishable from GroEL alone, and also those with consistent identifiable differences. Side-views of the modified particles reveal additional protein density at one end of the GroEL-GS complex, and end-views display chirality in the heptameric projection not seen in the unliganded GroEL. The coordinate appearance of these two projection differences suggests that binding of GS, as representative of a class of protein substrates, induces or stabilizes a conformation of GroEL that differs from the unliganded chaperonin. Three-dimensional reconstruction of the GroEL-GS complex reveals the location of the bound protein substrate, as well as complex conformational changes in GroEL itself, both cis and trans with respect to the bound GS. The most apparent structural alterations are inward movements of the apical domains of both GroEL heptamers, protrusion of the substrate protein from the cavity of the cis ring, and a narrowing of the unoccupied opening of the trans ring. Copyright 2001 Academic Press.
机译：在没有核苷酸或辅因子的情况下，大肠杆菌伴侣蛋白GroEL以非天然构象结合选择的蛋白质，例如变性的谷氨酰胺合成酶（GS）单体，从而防止了它们的聚集和自发复性。如此形成的GroEL-GS复合物的性质，特别是对GroEL四癸酰胺构象的影响已通过电子显微镜检查。我们发现，由于GroEL与GS的加载不完全，GroEL-GS的标本明显异质。图像包含与单独的GroEL不能区别的颗粒，以及具有一致的可识别差异的颗粒。修饰后的颗粒的侧视图显示了GroEL-GS复合物一端的额外蛋白质密度，而端面视图则显示了在未配体的GroEL中看不到的七聚体投影中的手性。这两个投影差异的坐标外观表明，作为一类蛋白质底物的代表，GS的结合可诱导或稳定不同于未结合的伴侣蛋白的GroEL构象。 GroEL-GS复合物的三维重建揭示了结合蛋白底物的位置，以及GroEL本身相对于结合GS的顺式和反式复合物构象变化。最明显的结构变化是两个GroEL七聚体的顶端结构域向内移动，底物蛋白从顺式环腔中突出以及反式环的未占用开口变窄。版权所有2001学术出版社。

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