Conformation of alamethicin in oriented phospholipid bilayers determined by 15N solid-state nuclear magnetic resonance
Conformation of alamethicin in oriented phospholipid bilayers determined by 15N solid-state nuclear magnetic resonance
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DOI：
10.1016/s0006-3495(01)75822-5
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发表时间：
2001-09-01
影响因子：
3.4
通讯作者：
Nielsen, NC
中科院分区：
文献类型：
--
作者：
Bak, M;Bywater, RP;Nielsen, NC
使用 N-15 固态核磁共振 (NMR) 光谱结合分子建模和分子动力学模拟，研究了宏观定向磷脂双层中 20 残基抗生素离子载体阿拉甲辛的构象。不同 N-15 标记的阿拉甲星变体以及三个 α-氨基异丁酸残基被丙氨酸取代的类似物已被研究，以建立实验结构约束并确定阿拉甲星在水合磷脂（二肉豆蔻酰磷脂酰胆碱）双层中的方向；并研究中央 Pro(14) 残基区域发生主要扭结的可能性。根据在 Ala(6)、Val(9) 和 Val(15) 残基上进行 N-15 标记并以 1:8 的肽：脂质摩尔比掺入磷脂双层中的阿拉甲辛测定的各向异性 N-15 化学位移和 H-1-N-15 偶极偶合，我们推断阿拉甲辛具有跨越 膜的分子轴相对于双层法线倾斜 10-20 度。特别是，我们发现与相对于双层法线倾斜 17 度的直 a 螺旋和倾斜 11 度的轻微扭结的分子动力学结构兼容。相反，由固态NMR导出的结构约束似乎与倾斜角消失的跨膜模型结构或早期报道的X射线衍射结构中的任何一个都不兼容（Fox和Richards，Nature.300：325-330，1982）。固态NMR兼容结构可以支持左手和平行多聚离子通道的形成。
The conformation of the 20-residue antibiotic ionophore alamethicin in macroscopically oriented phospholipid bilayers has been studied using N-15 solid-state nuclear magnetic resonance (NMR) spectroscopy in combination with molecular modeling and molecular dynamics simulations. Differently N-15-labeled variants of alamethicin and an analog with three of the a-amino-isobutyric acid residues replaced by alanines have been investigated to establish experimental structural constraints and determine the orientation of alamethicin in hydrated phospholipid (dimyristoylphosphatidylcholine) bilayers; and to investigate the potential for a major kink in the region of the central Pro(14) residue. From the anisotropic N-15 chemical shifts and H-1-N-15 dipolar couplings determined for alamethicin with N-15-labeling on the Ala(6), Val(9), and Val(15) residues and incorporated into phospholipid bilayer with a peptide:lipid molar ratio of 1:8, we deduce that alamethicin has a largely linear a-helical structure spanning the membrane with the molecular axis tilted by 10-20 degrees relative to the bilayer normal. In particular, we find compatibility with a straight a-helix tilted by 17 degrees and a slightly kinked molecular dynamics structure tilted by 11 degrees relative to the bilayer normal. In contrast, the structural constraints derived by solid-state NMR appear not to be compatible with any of several model structures crossing the membrane with vanishing tilt angle or the earlier reported x-ray diffraction structure (Fox and Richards, Nature. 300:325-330, 1982). The solid-state NMR-compatible structures may support the formation of a left-handed and parallel multimeric ion channel.