Vonderviszt F, Sonoyama M, Tasumi M, Namba K
ERATO, Molecular Dynamic Assembly Project, Tsukuba, Japan.
Biophys J. 1992 Dec;63(6):1672-7. doi: 10.1016/S0006-3495(92)81751-4.
Secondary structure formation in the disordered terminal regions of flagellin were studied by circular dichroic (CD) spectroscopy, Fourier transform infrared spectroscopy, and x-ray diffraction. The terminal regions of flagellin are known to form alpha-helical bundles upon polymerization into flagellar filaments. We found from comparative CD studies of flagellin and its F40 tryptic fragment that a highly alpha-helical conformation can be induced and stabilized in the terminal regions in 2,2,2-trifluoroethanol (TFE) containing solutions, which is known to promote intra-molecular hydrogen bonding. Two oligopeptides, N(37-61) and C(470-494), each corresponding to a portion of terminal regions and predicted to have a high alpha-helix forming potential, were synthesized and studied. Both peptides were disordered in an aqueous environment, but they showed a strong tendency to assume alpha-helical structure in solutions containing TFE. On the other hand, peptides were found to form transparent gels at high concentrations (> 15 mg/ml) and all three methods confirmed that the peptides become ordered into a predominantly beta structure upon gel formation. Our results show that large segments of the disordered terminal regions of flagellin can adopt alpha-helical as well as beta structure depending on the environmental conditions. This high degree of conformational adaptability may be reflecting some unique characteristics of the flagellin termini, which are involved in self-assembly and polymorphism of flagellar filament.
通过圆二色（CD）光谱、傅里叶变换红外光谱和X射线衍射研究了鞭毛蛋白无序末端区域的二级结构形成。已知鞭毛蛋白的末端区域在聚合成鞭毛丝时会形成α-螺旋束。我们通过对鞭毛蛋白及其F40胰蛋白酶片段的比较CD研究发现，在含有2,2,2-三氟乙醇（TFE）的溶液中，鞭毛蛋白的末端区域可以诱导并稳定形成高度α-螺旋构象，已知TFE可促进分子内氢键形成。合成并研究了两种寡肽，N(37 - 61)和C(470 - 494)，它们分别对应于末端区域的一部分，预计具有较高的α-螺旋形成潜力。两种肽在水性环境中都是无序的，但在含有TFE的溶液中它们表现出强烈的形成α-螺旋结构的倾向。另一方面，发现这些肽在高浓度（> 15 mg/ml）时会形成透明凝胶，并且所有三种方法都证实，肽在凝胶形成时会有序排列成主要为β结构。我们的结果表明，鞭毛蛋白无序末端区域的大部分可以根据环境条件采用α-螺旋结构以及β结构。这种高度的构象适应性可能反映了鞭毛蛋白末端的一些独特特征，这些特征与鞭毛丝的自组装和多态性有关。
