Dynamics of the C-terminal region of TnI in the troponin complex in solution
Dynamics of the C-terminal region of TnI in the troponin complex in solution
复制标题
DOI：
10.1529/biophysj.105.076216
复制
发表时间：
2006-04-01
影响因子：
3.4
通讯作者：
Sykes, BD
中科院分区：
文献类型：
--
作者：
Blumenschein, TMA;Stone, DB;Sykes, BD
肌钙蛋白复合物晶体结构的测定（Takeda et al. 2003.自然424：35-41; Vinogradova等人，2005. Proc. Natl. Acad. Sci. USA. 102：5038-5043）具有在分子水平上调节肌肉收缩的先进知识。然而，有领域的肌动蛋白结合的重要性是不可见的。我们提出的证据表明，肌钙蛋白I（TnI残基135-182）的C-末端区域是灵活的解决方案，并没有稳定的二级结构。我们用核磁共振波谱法观察了在Ca（2+）或EGTA/Mg（2+）存在下，肌钙蛋白复合物中[（2）H，（13）C，（15）N]-TnI骨架的动力学。该区域中的残基比TnI的其余部分给出更强的信号，并且化学位移指数值指示很少的二级结构，表明非常灵活的区域。这通过NMR弛豫测量证实。与复合物中的TnC和TnI的其他区域不同，TnI的C-末端区域不受Ca（2+）结合的影响。弛豫测量和降低的谱密度分析与TnI的C-末端区域一致，TnI是通过柔性接头残基137-146连接到肌钙蛋白复合物其余部分的拴系结构域，随后是具有至多新生二级结构的塌陷区域。
The determination of crystal structures of the troponin complex (Takeda et al. 2003. Nature. 424: 35-41; Vinogradova et al. 2005. Proc. Natl. Acad. Sci. USA. 102: 5038-5043) has advanced knowledge of the regulation of muscle contraction at the molecular level. However, there are domains important for actin binding that are not visualized. We present evidence that the C-terminal region of troponin I (TnI residues 135-182) is flexible in solution and has no stable secondary structure. We use NMR spectroscopy to observe the backbone dynamics of skeletal [(2)H, (13)C, (15)N]-TnI in the troponin complex in the presence of Ca(2+) or EGTA/Mg(2+). Residues in this region give stronger signals than the remainder of TnI, and chemical shift index values indicate little secondary structure, suggesting a very flexible region. This is confirmed by NMR relaxation measurements. Unlike TnC and other regions of TnI in the complex, the C-terminal region of TnI is not affected by Ca(2+) binding. Relaxation measurements and reduced spectral density analysis are consistent with the C-terminal region of TnI being a tethered domain connected to the rest of the troponin complex by a flexible linker, residues 137-146, followed by a collapsed region with at most nascent secondary structure.