Investigating the effects of tropomyosin mutations on its flexibility and interactions with filamentous actin using molecular dynamics simulation
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- 作者：Wenjun Zheng ; Sarah E. Hitchcock-DeGregori…
- 关键词：Binding energy ; Cardiomyopathy ; F ; actin ; Flexibility ; Molecular dynamics ; Mutation ; Persistent length ; Tropomyosin
- 刊名：Journal of Muscle Research and Cell Motility
- 出版年：2016
- 出版时间：October 2016
- 年：2016
- 卷：37
- 期：4-5
- 页码：131-147
- 全文大小：1,915 KB
- 刊物主题：Cell Biology; Proteomics; Animal Anatomy / Morphology / Histology; Biomedicine general;
- 出版者：Springer Netherlands
- ISSN：1573-2657
- 卷排序：37
文摘
Tropomyosin (Tpm) is a two-chained α-helical coiled-coil protein that binds to filamentous actin (F-actin), and regulates its interactions with myosin by occupying three average positions on F-actin (blocked, closed, and open). Mutations in the Tpm are linked to heart diseases including hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). To elucidate the molecular mechanisms of Tpm mutations (including DCM mutation E54K, HCM mutations E62Q, A63V, K70T, V95A, D175N, E180G, L185R, E192K, and a designed synthetic mutation D137L) in terms of their effects on Tpm flexibility and its interactions with F-actin, we conducted extensive molecular dynamics simulations for the wild-type and mutant Tpm in complex with F-actin (total simulation time 160 ns per mutant). The mutants exhibited distinct changes (i.e., increase or decrease) in the overall and local flexibility of the Tpm coiled-coil, with each mutation causing both local and long-range modifications of the Tpm flexibility. In addition, our binding calculations revealed weakened Tpm–F-actin interactions (except for L185R, D137L and A63V) involving five periods of Tpm, which correlate with elevated fluctuation of Tpm relative to the blocked position on F-actin that may lead to easier activation and increased Ca2+-sensitivity. We also simulated the αβ/βα-Tpm heterodimer in comparison with the αα-Tpm homodimer, which revealed greater flexibility and weaker actin binding in the heterodimer. Our findings are consistent with a complex mechanism underlying how different Tpm mutations perturb the Tpm function in distinct ways (e.g., by affecting specific sites of Tpm), which bear no simple links to the disease phenotypes (e.g., HCM vs. DCM).