Two-state expansion and collapse of a polypeptide
Two-state expansion and collapse of a polypeptide
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DOI：
10.1006/jmbi.2000.3969
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发表时间：
2000-08-25
影响因子：
5.6
通讯作者：
Eaton, WA
中科院分区：
文献类型：
--
作者：
Hagen, SJ;Eaton, WA
许多蛋白质折叠的初始阶段被认为是多肽链从膨胀到紧凑但仍变性的构象的崩溃。理论和模拟表明，这种崩溃可能是一个两态转变，其特征是跨越障碍动力学，而均聚物的崩溃是连续的和多相的。我们采用激光温度跳变与荧光光谱技术，以纳秒级的时间分辨率测量了变性细胞色素c坍缩的完整时间过程。我们发现该过程在时间和热激活方面呈指数型，表观活化能类似于9 k(B)T（经溶剂粘度校正后）。这些结果表明多肽塌缩在动力学上是一个两态转变。由于观察到的自由能势垒，多肽塌缩的时间尺度比均聚物塌缩的朗格万模型预测的要慢得多。
The initial phase of folding for many proteins is presumed to be the collapse of the polypeptide chain from expanded to compact but still denatured, conformations. Theory and simulations suggest that this collapse may be a two-state transition, characterized by barrier-crossing kinetics, while the collapse of homopolymers is continuous and multiphasic. We have used laser temperature-jump with fluorescence spectroscopy to measure the complete time-course of the collapse of denatured cytochrome c with nanosecond time resolution. We find the process to be exponential in time and thermally activated, with an apparent activation energy similar to 9 k(B)T (after correction for solvent viscosity). These results indicate that polypeptide collapse is kinetically a two-state transition. Because of the observed free energy barrier, the time scale of polypeptide collapse is dramatically slower than is predicted by Langevin models for homopolymer collapse.