Transient, sparsely populated compact states of apo and calcium-loaded calmodulin probed by paramagnetic relaxation enhancement: interplay of conformational selection and induced fit.
Transient, sparsely populated compact states of apo and calcium-loaded calmodulin probed by paramagnetic relaxation enhancement: interplay of conformational selection and induced fit.
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DOI：
10.1021/ja2082813
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发表时间：
2011-11-23
影响因子：
15
通讯作者：
Clore, G. Marius
中科院分区：
文献类型：
--
作者：
Anthis, Nicholas J.;Doucleff, Michaeleen;Clore, G. Marius
钙调素(CaM)是真核生物中普遍存在的钙感受器，调节多种蛋白质的功能。结晶学和核磁共振研究表明，游离的CaM-4Ca~(2+)以延伸的构象形式存在，存在显著的结构域间分离，但能抑制目标多肽形成高度致密的结构。核磁共振显示CaM-4Ca~(2+)在柔性连接体的作用下发生了实质性的域间运动。在一个例子中，CaM-4Ca~(2+)以致密的构型结晶；然而，在溶液中没有观察到瞬时结构域间接触的直接证据，也几乎不知道大规模结构域间运动如何对生物功能做出贡献。在这里，我们使用顺磁弛豫增强(PRE)来表征自由CaM的瞬时紧凑状态，这些状态太稀疏，无法用传统的核磁共振方法观察到。我们表明，未结合的CaM样本了一系列紧凑的结构，填充在5-10%，而钙离子显著改变了这些配置的分布，有利于类似于肽结合结构的状态。在无Ca~(2+)的情况下，靶肽仅与C-末端结构域结合，致密态分布与无肽相似。这些数据提示了CaM作用的另一种途径，在该途径中，即使在静息状态下，CaM仍与其激酶靶标相关联。然而，只有CaM-4Ca~(2+)表现出天生的形成生理活性紧凑结构的倾向，这表明Ca~(2+)不仅通过每个结构域的局部结构变化激活CaM，而且还通过更全面的域间相互作用的重塑来激活CaM。因此，这些发现说明了构象选择和诱导匹配之间微妙的相互作用。
Calmodulin (CaM) is the universal calcium sensor in eukaryotes, regulating the function of numerous proteins. Crystallography and NMR show that free CaM-4Ca2+ exists in an extended conformation with significant interdomain separation, but clamps down upon target peptides to form a highly compact structure. NMR has revealed substantial interdomain motions in CaM-4Ca2+, enabled by a flexible linker. In one instance, CaM-4Ca2+ has been crystallized in a compact configuration; however, no direct evidence for transient interdomain contacts has been observed in solution, and little is known about how large-scale interdomain motions contribute to biological function. Here we use paramagnetic relaxation enhancement (PRE) to characterize transient compact states of free CaM that are too sparsely populated to observe by traditional NMR methods. We show that unbound CaM samples a range of compact structures, populated at 5–10%, and that Ca2+ dramatically alters the distribution of these configurations in favor of states resembling the peptide-bound structure. In the absence of Ca2+, the target peptide binds only to the C-terminal domain, and the distribution of compact states is similar with and without peptide. These data suggest an alternative pathway of CaM action in which CaM remains associated with its kinase targets even in the resting state. Only CaM-4Ca2+, however, shows an innate propensity to form the physiologically active compact structures, suggesting that Ca2+ activates CaM not only through local structural changes within each domain but also through more global remodeling of interdomain interactions. Thus, these findings illustrate the subtle interplay between conformational selection and induced fit.
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影响因子：
2.2
作者：
Hu, Kaifeng;Doucleff, Michaeleen;Clore, G. Marius
通讯作者：
Clore, G. Marius
影响因子：
56.9
作者：
IKURA, M;CLORE, GM;BAX, A
通讯作者：
BAX, A
影响因子：
8
作者：
Bayley, PM;Findlay, WA;Martin, SR
通讯作者：
Martin, SR
影响因子：
15
作者：
Baber, JL;Szabo, A;Tjandra, N
通讯作者：
Tjandra, N
影响因子：
2.7
作者：
Dasgupta, Soumyasri;Hu, Xiaoyu;Ubbink, Marcellus
通讯作者：
Ubbink, Marcellus