The α-helix folds on the millisecond time scale
The α-helix folds on the millisecond time scale
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DOI：
10.1073/pnas.96.13.7232
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发表时间：
1999-06-22
影响因子：
11.1
通讯作者：
Jones, GR
中科院分区：
文献类型：
--
作者：
Clarke, DT;Doig, AJ;Jones, GR
长期以来，人们一直相信α-螺旋的成核是一个非常快的反应，大约发生在10(-7)S左右。我们在这里证明了螺旋的成核实际上发生在毫秒级的时间尺度上。以同步辐射为光源的停流深紫外光CD直接测量两种聚丙氨酸多肽以及赖氨酸和谷氨酸均聚物中的α-螺旋成核速率。与传统仪器相比，同步辐射CD的信号噪声比要高得多。16-AA AK多肽在0℃下折叠符合一级动力学，速率常数为15 S(-1)，速率决定步骤可能是新螺旋的启动，其发生速度至少比预期慢10(5)Lims，对于较长的多肽，螺旋折叠在毫秒时间尺度上至少分两步进行，螺旋含量的瞬时超调量显著大于平衡状态，与几种蛋白质的折叠类似。我们认为，超调是由单个长螺旋的形成，然后它断裂成两个或更多处于平衡状态的螺旋造成的。
It has long been belie, ed that nucleation of the alpha-helix is a very fast reaction, occurring in around 10(-7) s. We show here that helix nucleation, in fact, takes place on the millisecond time scale. The rate of alpha-helix nucleation in two polyalanine-based peptides and in lysine and glutamic acid homopolymers,vas measured directly by stopped-flow deep UV CD with synchrotron radiation as the light source. Synchrotron radiation CD gives far superior signal to noise than a conventional instrument. The 16-aa AK peptide folds with first-order kinetics and a rate constant of 15 s(-1) at 0 degrees C, The rate-determining step is presumably the initiation of a new helix, which occurs at least 10(5) Limes slower than expected, Helix folding occurs in at least two steps on the millisecond time scale for the longer peptides, with a transient overshoot of helix content significantly greater than at equilibrium, similar to that seen in the folding of several proteins. We suggest that the overshoot is caused by the formation of a single long helix followed by its breakage into the two or more helices present at equilibrium.