Wallace B A
Biophys J. 1986 Jan;49(1):295-306. doi: 10.1016/S0006-3495(86)83642-6.
Gramicidin A, a hydrophobic linear polypeptide, forms channels in phospholipid membranes that are specific for monovalent cations. Nuclear Magnetic Resonance (NMR) spectroscopy provided the first direct physical evidence that the channel conformation in membranes is an amino terminal-to-amino terminal helical dimer, and circular dichroism (CD) spectroscopy has shown the sensitivity of its conformation to different environments and the structural consequences of ion binding. The three-dimensional structure of a gramicidin/cesium complex has been determined by x-ray diffraction of single crystals using single wavelength anomalous scattering for phasing. The left-handed double helix in this crystal form corresponds to one of the intermediates in the process of folding and insertion into membranes. Co-crystals of gramicidin and lipid that appear to have gramicidin in their membrane channel conformation have also been formed and are presently under investigation. Hence, we have used a combination of spectroscopic and diffraction techniques to examine the conformation and functionally-related structural features of gramicidin A.
短杆菌肽A是一种疏水性线性多肽，可在磷脂膜中形成对单价阳离子具有特异性的通道。核磁共振（NMR）光谱提供了首个直接的物理证据，表明膜中的通道构象是氨基端到氨基端的螺旋二聚体，而圆二色性（CD）光谱则显示了其构象对不同环境的敏感性以及离子结合的结构后果。短杆菌肽/铯复合物的三维结构已通过使用单波长反常散射进行相位测定的单晶X射线衍射确定。这种晶体形式的左手双螺旋对应于折叠和插入膜过程中的中间体之一。短杆菌肽与脂质的共晶体似乎在其膜通道构象中含有短杆菌肽，并且目前正在研究中。因此，我们结合了光谱学和衍射技术来研究短杆菌肽A的构象和功能相关的结构特征。
