Specific collapse followed by slow hydrogen-bond formation of β-sheet in the folding of single-chain monellin
Specific collapse followed by slow hydrogen-bond formation of β-sheet in the folding of single-chain monellin
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DOI：
10.1073/pnas.0407982102
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发表时间：
2005-02-22
影响因子：
11.1
通讯作者：
Fujisawa, T
中科院分区：
文献类型：
--
作者：
Kimura, T;Uzawa, T;Fujisawa, T
具有不同二级结构的蛋白质的构象景观的表征对于阐明蛋白质折叠的机制是重要的。利用pH跃变法研究了由五股β折叠和一个螺旋组成的单链莫内林蛋白从碱性展开到天然状态的折叠轨迹。二级结构和整体大小和形状的动力学变化分别通过圆二色谱和小角X-射线散射测量。通过内源和外源荧光监测三级结构的形成。一个显着的崩溃后300 μ s内观察到的pH值的跳跃，导致少量的二级和三级结构，但与整体扁圆形的中间体。随后，检测到二级和三级结构的逐步形成。目前的观察结果与理论预测一致，即在β-折叠蛋白的折叠中比螺旋蛋白的折叠中在二级结构形成之前有更显著的塌陷[Shea，J.E.，Onuchic，J. N. &布鲁克斯，C. L.，III（2002）Proc. Nati. Acad. Sci. USA 99，16064-16068]。此外，这意味着，一些特定的结构元素，如急转弯，形成扁圆形的形成，促进了初始崩溃。
Characterization of the conformational landscapes for proteins with different secondary structures is important in elucidating the mechanism of protein folding. The folding trajectory of single-chain monellin composed of a five-stranded beta-sheet and a helix was investigated by using a pH-jump from the alkaline unfolded to native state. The kinetic changes in the secondary structures and in the overall size and shape were measured by circular dichroism spectroscopy and small-angle x-ray scattering, respectively. The formation of the tertiary structure was monitored by intrinsic and extrinsic fluorescence. A significant collapse was observed within 300 mus after the pH-jump, leading to the intermediate with a small amount of secondary and tertiary structures but with an overall oblate shape. Subsequently, the stepwise formation of secondary and tertiary structures was detected. The current observation was consistent with the theoretical prediction that a more significant collapse precedes the formation of secondary structures in the folding of beta-sheet proteins than that of helical proteins [Shea, J. E., Onuchic, J. N. & Brooks, C. L., III (2002) Proc. Nati. Acad. Sci. USA 99, 16064-16068]. Furthermore, it was implied that the initial collapse was promoted by the formation of some specific structural elements, such as tight turns, to form the oblate shape.