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首页> 外文期刊>Biochemistry >NMR SOLUTION STRUCTURE OF A SYNTHETIC TROPONIN C HETERODIMERIC DOMAIN
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NMR SOLUTION STRUCTURE OF A SYNTHETIC TROPONIN C HETERODIMERIC DOMAIN

机译：合成肌钙蛋白C异二聚体域的NMR溶液结构

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摘要

The C-terminal domain from the muscle protein troponin C (TnC) comprises two helix-loop-helix calcium-binding sites (residues 90-162). The assembly of these two sites is governed by calcium binding enabling a synthetic C-terminal domain to be preferentially and stoichiometrically assembled from two synthetic peptides (residues 93-126, SCIII, and 129-162, SCIV) in the presence of calcium only. It is therefore of great interest to know how closely the structure of this heterodimeric domain is to the intact protein domain. Analysis of such a structure has important implications in protein engineering and in understanding the stability of calcium-binding proteins in terms of biological function. The solution structure of this heterodimeric protein was determined by H-1 NMR spectroscopy using 802 NOE derived distance restraints and 23 phi and 22 chi(1) angle restraints. Distance geometry-simulated annealing calculations yielded a family of 42 converged structures (rmsd 0.86 +/- 0.17 Angstrom) showing an arrangement of four a-helices similar in fold to the C-terminal of troponin C. The dimer interface has several important interactions between helix pairs E/H and F/G responsible for the association of the two peptides. However, neither the peptide complex nor the solution NMR structure of TnC pack as tightly as that observed in the TnC X-ray structure. The interhelical distance between the F/G helix is about 1.4 Angstrom greater in solution than in the crystal. A comparison of the exposed surface area of the hydrophobic residues in the SCIII/SCIV heterodimer revealed that residues I104, Y112, and I121 are more exposed than in the previously determined solution structure of the SCIII homodimer. These residues are important for the interaction with the inhibitory region of TnI and provide evidence for their involvement in the regulation of muscle contraction.
机译：肌钙蛋白C（TnC）的C末端结构域包含两个螺旋-环-螺旋钙结合位点（残基90-162）。这两个位点的组装受钙结合的支配，使合成的C末端结构域可以在钙的存在下优先和化学计量地由两个合成肽（残基93-126，SCIII和129-162，SCIV）组装。因此，非常感兴趣的是知道该异二聚体结构域的结构与完整蛋白结构域的紧密程度。对这种结构的分析在蛋白质工程和理解钙结合蛋白的生物学功能稳定性方面具有重要意义。通过使用802 NOE衍生的距离限制以及23 phi和22 chi（1）角度限制的H-1 NMR光谱测定此异二聚体蛋白质的溶液结构。距离几何学模拟的退火计算得出了42个会聚结构的族（均方根0.86 +/- 0.17埃），显示了与肌钙蛋白C的C端折叠相似的四个a螺旋的排列。二聚体界面之间存在一些重要的相互作用负责两个肽缔合的螺旋对E / H和F / G。但是，TnC的肽复合物和溶液NMR结构都没有像在TnC X射线结构中观察到的那样紧密。在溶液中，F / G螺旋之间的螺旋间距大约比晶体中的螺旋间距大1.4埃。比较SCIII / SCIV异二聚体中疏水残基的暴露表面积，可以发现残基I104，Y112和I121比SCIII同二聚体的先前确定的溶液结构暴露更多。这些残基对于与TnI抑制区的相互作用很重要，并为它们参与调节肌肉收缩提供了证据。

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