FTIR Spectroscopy of secondary-structure reorientation of melibiose permease modulated by substrate binding
FTIR Spectroscopy of secondary-structure reorientation of melibiose permease modulated by substrate binding
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DOI：
10.1529/biophysj.107.115550
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发表时间：
2008-05-01
影响因子：
3.4
通讯作者：
Padros, Esteve
中科院分区：
文献类型：
--
作者：
Dave, Natalia;Lorenz-Fonfria, Victor A.;Padros, Esteve
对来自大肠杆菌的重构蜜二糖渗透酶的红外偏振吸收光谱和线性二色性光谱的分析表明，定向结构主要对应于倾斜的跨膜α螺旋，与无底物介质中的膜法线形成类似于26度的平均角度。对 H2O 和 D2O 中的解卷积线性二色性光谱的检查可以明显看出两个 α 螺旋群的倾斜角不同（螺旋类型 I 和 II）。此外，平均螺旋倾角随底物结合而显着变化：当Na+结合时平均螺旋倾角增加，而当Na+存在时随后的蜜二糖结合时平均螺旋倾角减小。相比之下，在 H+ 存在的情况下，蜜二糖结合几乎不会导致平均倾斜角发生变化。数据还表明，两个螺旋群根据结合底物以不同方式改变其倾斜和 H/D 交换水平。值得注意的是，阳离子结合本质上影响 I 型螺旋，而蜜二糖结合改变两个螺旋群的倾斜。
Analysis of infrared polarized absorbance spectra and linear dichroism spectra of reconstituted melibiose permease from Escherichia coli shows that the oriented structures correspond mainly to tilted transmembrane alpha- helices, forming an average angle of similar to 26 degrees with the membrane normal in substrate- free medium. Examination of the deconvoluted linear dichroism spectra in H2O and D2O makes apparent two populations of alpha- helices differing by their tilt angle ( helix types I and II). Moreover, the average helical tilt angle significantly varies upon substrate binding: it is increased upon Na+ binding, whereas it decreases upon subsequent melibiose binding in the presence of Na+. In contrast, melibiose binding in the presence of H+ causes virtually no change in the average tilt angle. The data also suggest that the two helix populations change their tilting and H/ D exchange level in different ways depending on the bound substrate(s). Notably, cation binding essentially influences type I helices, whereas melibiose binding modifies the tilting of both helix populations.