Dynamics of the transition between open and closed conformations in a calmodulin C-terminal domain mutant
Dynamics of the transition between open and closed conformations in a calmodulin C-terminal domain mutant
复制标题
DOI：
10.1016/s0969-2126(01)00575-5
复制
发表时间：
2001-03-07
期刊：
影响因子：
5.7
通讯作者：
Akke, M
中科院分区：
文献类型：
--
作者：
Evenäs, J;Malmendal, A;Akke, M
背景：钙调蛋白是真核生物细胞过程中普遍存在的 Ca2+ 激活调节剂。钙调蛋白的无 Ca2+ (apo) 和负载 Ca2+ 状态的结构表明，Ca2+ 结合与两个结构域中的每一个结构域从封闭构象到开放构象的转变有关，而开放构象是目标识别的核心。然而，人们对这种构象转换的动力学知之甚少。结果：在平衡条件下表征了钙调蛋白C端结构域E140Q突变体的Ca2+加载状态下闭合构象和开放构象之间转变的动力学。测量的 42 个残基的交换时间常数 (tau (ex)) 范围为 13 至 46 mus，平均值为 21 +/- 3 mu。结果表明，不同残基组之间的 tau (ex) 差异显着，并且具有相似值的残基在 apo 和/或 Ca2+ 饱和野生型钙调蛋白的结构中表现出空间接近性。使用其中一组的数据，我们获得了 p(o) = 0.50 +/- 0.17 的开放群体和 k(o) = (2.7 +/- 1.0) x 10(4) s(-1) 的封闭 --> 开放速率常数。结论：构象交换动力学似乎涉及依赖于结构拓扑的局部集体过程。与之前的结果比较表明，野生型蛋白质中也发生了类似的过程。测量的速率与估计的 Ca2+ 解离速率相匹配，表明 Ca2+ 释放可能由构象动力学控制。对估计化学位移的结构解释表明了离子释放的机制。
Background: Calmodulin is a ubiquitous Ca2+-activated regulator of cellular processes in eukaryotes. The structures of the Ca2+-free (apo) and Ca2+-loaded states of calmodulin have revealed that Ca2+ binding is associated with a transition in each of the two domains from a closed to an open conformation that is central to target recognition. However, little is known about the dynamics of this conformational switch.Results: The dynamics of the transition between closed and open conformations in the Ca2+-loaded state of the E140Q mutant of the calmodulin C-terminal domain were characterized under equilibrium conditions. The exchange time constants (tau (ex)) measured for 42 residues range from 13 to 46 mus, with a mean of 21 +/- 3 mus. The results suggest that tau (ex) varies significantly between different groups of residues and that residues with similar values exhibit spatial proximity in the structures of apo and/or Ca2+-saturated wild-type calmodulin. Using data for one of these groups, we obtained an open population of p(o) = 0.50 +/- 0.17 and a closed --> open rate constant of k(o) = (2.7 +/- 1.0) x 10(4) s(-1).Conclusions: The conformational exchange dynamics appear to involve locally collective processes that depend on the structural topology. Comparisons with previous results indicate that similar processes occur in the wild-type protein. The measured rates match the estimated Ca2+ off rate, suggesting that Ca2+ release may be gated by the conformational dynamics. Structural interpretation of estimated chemical shifts suggests a mechanism for ion release.