Fast events in protein folding: Helix melting and formation in a small peptide
Fast events in protein folding: Helix melting and formation in a small peptide
复制标题
DOI：
10.1021/bi952217p
复制
发表时间：
1996-01-23
期刊：
影响因子：
2.9
通讯作者：
Dyer, RB
中科院分区：
文献类型：
--
作者：
Williams, S;Causgrove, TP;Dyer, RB
螺旋是蛋白质中常见的二级结构基序，螺旋-螺旋相互转换的机制是理解蛋白质折叠问题的关键。我们报道了在一个小的21个丙氨酸残基的多肽中观察到的螺旋熔化的快速动力学(纳秒到毫秒)。去折叠反应是通过激光诱导的温度跳跃启动的，并使用时间分辨红外光谱进行探测。该模型肽具有快速的去折叠动力学，在28℃下的时间常数为160+/-60 ns，响应于激光诱导的18℃的温度跃升，该过程在20 ns内完成。根据模型肽的展开时间和测得的螺旋-螺旋平衡常数，可以推断出28℃下螺旋形成反应的折叠速率常数约为6×10(7)S(-1)(t(1/2)=16 ns)。这些结果表明，二级结构的形成足够快，足以成为蛋白质折叠过程中的早期关键事件，并且螺旋能够在长距离三级接触之前形成。
The helix is a common secondary structural motif found in proteins, and the mechanism of helix-coil interconversion is key to understanding the protein-folding problem. We report the observation of the fast kinetics (nanosecond to millisecond) of helix melting in a small 21-residue alanine-based peptide. The unfolding reaction is initiated using a laser-induced temperature jump and probed using time-resolved infrared spectroscopy. The model peptide exhibits fast unfolding kinetics with a time constant of 160 +/- 60 ns at 28 degrees C in response to a laser-induced temperature jump of 18 degrees C which is completed within 20 ns. Using the unfolding time and the measured helix-coil equilibrium constant of the model peptide, a folding rate constant of approximately 6 x 10(7) s(-1) (t(1/2) = 16 ns) can be inferred for the helix formation reaction at 28 degrees C. These results demonstrate that secondary structure formation is fast enough to be a key event at early times in the protein-folding process and that helices are capable of forming before long range tertiary contacts are made.