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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Validation of the single-stranded channel conformation of gramicidin A by solid-state NMR
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Validation of the single-stranded channel conformation of gramicidin A by solid-state NMR

机译：固态核磁共振验证短杆菌肽A的单链通道构象

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摘要

The monovalent cation selective channel formed by a dimer of the polypeptide gramicidin A has a single-stranded, right-handed helical motif with 6.5 residues per turn forming a 4-A diameter pore. The structure has been refined to high resolution against 120 orientational constraints obtained from samples in a liquid-crystalline phase lipid bilayer. These structural constraints from solid-state NMR reflect the orientation of spin interaction tensors with respect to a unique molecular axis. Because these tensors are fixed in the molecular frame and because the samples are uniformly aligned with respect to the magnetic field of the MNR spectrometer, each constraint restricts the orientation of internuclear vectors with respect to the laboratory frame of reference. The structural motif of this channel has been validated, and the high-resolution structure has led to precise models for cation binding, cation selectivity, and cation conductance efficiency. The structure is consistent with the electrophysiological data and numerous biophysical studies .Contrary to a recent claim,atge sikud-state NMR constraints for gramicidin A in a lipid bilayer are not consistent with an X-ray crystallographic structure for gramicidin having a double-stranded, right-handed helix with 7.2 residues per turn.
机译：由多肽短杆菌肽A的二聚体形成的单价阳离子选择性通道具有单链右旋螺旋基序，每匝具有6.5个残基，形成4-A直径的孔。针对从液晶相脂质双层中的样品获得的120个定向约束，该结构已进行了改进，以实现高分辨率。固态NMR的这些结构限制反映了自旋相互作用张量相对于唯一分子轴的方向。由于这些张量固定在分子框架中，并且由于样品相对于MNR光谱仪的磁场均匀排列，因此每个约束条件都限制了核间矢量相对于实验室参考框架的方向。该通道的结构基序已得到验证，高分辨率结构导致了阳离子结合，阳离子选择性和阳离子电导效率的精确模型。该结构与电生理数据和大量生物物理研究相一致。与最近的说法相反，脂双层中的短杆菌肽A的atik sikud状态NMR约束与短杆菌肽具有双链的X射线晶体学结构不一致，右旋螺旋，每转有7.2个残基。

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