Two-state expansion and collapse of a polypeptide
Two-state expansion and collapse of a polypeptide
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DOI：
10.1006/jmbi.2000.3508
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发表时间：
2000-03-31
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展开到紧凑但仍然变性的构象的塌陷。理论和模拟表明，这种塌缩可能是一种二态转变，其特征是跨越势垒动力学，而均聚物和无规杂聚物的塌缩是连续且多相的。一种新的快速混合流技术已被用来解决多肽崩溃的后期阶段，时间尺度大于或等于45μs。我们使用带有荧光光谱的激光跳温技术以纳秒时间分辨率解析变性细胞色素 c 崩溃的完整时间过程。我们发现该过程在时间和热激活方面呈指数关系，表观激活能类似于 9 k(B)T（在溶剂粘度校正后）。这些结果表明多肽崩溃在动力学上是一种两种状态的转变。由于观察到的自由能垒，多肽崩溃的时间尺度比朗之万均聚物崩溃模型预测的要慢得多。 (C) 2000 年学术出版社。
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 and random heteropolymers is continuous and multi-phasic. A new rapid-mixing flow technique has been used to resolve the late stages of polypeptide collapse,at time scales greater than or equal to 45 mu s. We have used a laser temperature-jump with fluorescence spectroscopy to resolve 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. (C) 2000 Academic Press.