Structural analysis of alanine tripeptide with antiparallel and parallel β-sheet structures in relation to the analysis of mixed β-sheet structures in Samia cynthia ricini silk protein fiber using solid-state NMR spectroscopy
Structural analysis of alanine tripeptide with antiparallel and parallel β-sheet structures in relation to the analysis of mixed β-sheet structures in Samia cynthia ricini silk protein fiber using solid-state NMR spectroscopy
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DOI：
10.1021/ja060251t
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发表时间：
2006-05-10
影响因子：
15
通讯作者：
Yamauchi, K
中科院分区：
文献类型：
--
作者：
Asakura, T;Okonogi, M;Yamauchi, K
报道了通过固态核磁共振对具有混合平行和反平行β-折叠结构的天然蛋白质纤维进行结构分析。为了获得能够表征这些 β-折叠结构的 NMR 参数，对两种丙氨酸三肽样品进行了 C-13 固态 NMR 实验：一种具有 100% 平行 β-折叠结构，另一种具有 100% 反平行 β-折叠结构。三肽的所有 C-13 共振可以通过比较 Ala(3) 的甲基 C-13 共振与不同的 [3-C-13] Ala 标记方案以及通过改变混合时间观察到的一系列 RFDR（射频驱动重偶联）光谱来分配。每个 Ala 残基观察到的两个 C-13 共振可以分配给每个晶胞的两个非等价分子。在两个 β-折叠结构之间观察到 C-13 化学位移和 C-13 自旋晶格弛豫时间 (T-1) 的差异。特别是，与反平行β-折叠结构相比，平行β-折叠结构获得了大约3倍长的T-1值，这可以通过两种结构的氢键网络的差异来解释。 T-1 的这种巨大差异成为区分平行或反平行 β-折叠结构的良好指标。三肽的 NMR 参数差异可用于确定野生蚕 Samia cynthia ricini 的 [3-C-13]-Ala 丝蛋白纤维的不对称和宽甲基光谱中的平行和反平行 β-折叠 C-13 共振。
The structural analysis of natural protein fibers with mixed parallel and antiparallel beta-sheet structures by solid-state NMR is reported. To obtain NMR parameters that can characterize these beta-sheet structures, C-13 solid-state NMR experiments were performed on two alanine tripeptide samples: one with 100% parallel beta-sheet structure and the other with 100% antiparallel beta-sheet structure. All C-13 resonances of the tripeptides could be assigned by a comparison of the methyl C-13 resonances of Ala(3) with different [3-C-13] Ala labeling schemes and also by a series of RFDR (radio frequency driven recoupling) spectra observed by changing mixing times. Two C-13 resonances observed for each Ala residue could be assigned to two nonequivalent molecules per unit cell. Differences in the C-13 chemical shifts and C-13 spin-lattice relaxation times (T-1) were observed between the two beta-sheet structures. Especially, about 3 times longer T-1 values were obtained for parallel beta-sheet structure as compared to those of antiparallel beta-sheet structure, which could be explicable by the difference in the hydrogen-bond networks of both structures. This very large difference in T-1 becomes a good measure to differentiate between parallel or antiparallel beta-sheet structures. These differences in the NMR parameters found for the tripeptides may be applied to assign the parallel and antiparallel beta-sheet C-13 resonances in the asymmetric and broad methyl spectra of [3-C-13]-Ala silk protein fiber of a wild silkworm, Samia cynthia ricini.