Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Alberta, Canada T2N 4Z6.
Biochemistry. 2012 Apr 3;51(13):2694-705. doi: 10.1021/bi2019018. Epub 2012 Mar 22.
The calponin homology-associated smooth muscle (CHASM) protein plays an important adaptive role in smooth and skeletal muscle contraction. CHASM is associated with increased muscle contractility and can be localized to the contractile thin filament via its binding interaction with tropomyosin. We sought to define the structural basis for the interaction of CHASM with smooth muscle tropomyosin as a first step to understanding the contribution of CHASM to the contractile capacity of smooth muscle. Herein, we provide a structure-based model for the tropomyosin-binding domain of CHASM using a combination of hydrogen/deuterium exchange mass spectrometry (HDX-MS) and NMR analyses. Our studies provide evidence that a portion of the N-terminal intrinsically disordered region forms intramolecular contacts with the globular C-terminal calponin homology (CH) domain. Ultimately, cooperativeness between these structurally dissimilar regions is required for CHASM binding to smooth muscle tropomyosin. Furthermore, it appears that the type-2 CH domain of CHASM is required for tropomyosin binding and presents a novel function for this protein domain.
钙调节蛋白同源相关平滑肌蛋白（CHASM）在平滑肌和骨骼肌收缩中起着重要的适应性作用。CHASM 与肌肉收缩力增加有关，通过与原肌球蛋白的结合相互作用可以定位于收缩性细肌丝。我们试图确定 CHASM 与平滑肌原肌球蛋白相互作用的结构基础，作为理解 CHASM 对平滑肌收缩能力贡献的第一步。在此，我们使用氢/氘交换质谱（HDX-MS）和 NMR 分析的组合，为 CHASM 的原肌球蛋白结合域提供了一个基于结构的模型。我们的研究提供了证据，证明一部分 N 端固有无序区与球状 C 端钙调节蛋白同源（CH）结构域形成分子内接触。最终，这些结构上不同的区域之间的协同作用对于 CHASM 与平滑肌原肌球蛋白的结合是必需的。此外，CHASM 的 CH 结构域类型 2似乎需要原肌球蛋白结合，并为该蛋白结构域呈现了一个新的功能。
