Membrane orientation of the N-terminal segment of alamethicin determined by solid-state N-15 NMR
Membrane orientation of the N-terminal segment of alamethicin determined by solid-state N-15 NMR
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DOI：
10.1016/s0006-3495(95)80108-6
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发表时间：
1995-12-01
影响因子：
3.4
通讯作者：
Cafiso, DS
中科院分区：
文献类型：
--
作者：
North, CL;BarrangerMathys, M;Cafiso, DS
合成丙甲霉素，其中N-15掺入肽序列中6位的丙氨酸中。在水合二肉豆蔻酰磷脂酰胆碱的分散体中，固态N-15 NMR产生轴对称的粉末图案，表明当与层状脂质相关联时，肽以单一对称轴重新定向。当掺入到双层法线平行于B-0场的均匀取向的双层中时，观察到的N-15化学位移的位置为171 ppm。这与非定向水合样品的轴对称粉末图案的西格玛（平行于）边缘一致。因此，运动平均的轴沿着双层法线。二维分离的局部场谱，提供了一个维度的N-H偶极耦合和N-15化学位移在其他的措施。这些数据产生17 kHz的偶极耦合，对应于N-H键相对于B-0场轴的平均角度为24度。可能的结构和方向，可以产生所观察到的光谱参数的分析表明，这些值是一致的α-螺旋构象插入沿着双层正常。
Alamethicin was synthesized with N-15 incorporated into alanine at position 6 in the peptide sequence. In dispersions of hydrated dimyristoylphosphatidylcholine, solid-state N-15 NMR yields an axially symmetric powder pattern indicating that the peptide is reorienting with a single axis of symmetry when associated with lamellar lipids. When incorporated into bilayers that are uniformly oriented with the bilayer normal parallel to the B-0 field, the position of the observed N-15 chemical shift is 171 ppm. This is coincident with the sigma(parallel to) edge of the axially symmetric powder pattern for non-oriented hydrated samples. Thus the axis of motional averaging lies along the bilayer normal. Two-dimensional separated local field spectra were obtained that provide a measure of the N-H dipolar coupling in one dimension and the N-15 chemical shift in the other. These data yield a dipolar coupling of 17 kHz corresponding to an average angle of 24 degrees for the N-H bond with respect to the B-0 field axis. An analysis of the possible structures and orientations that could produce the observed spectral parameters show that these values are consistent with an alpha-helical conformation inserted along the bilayer normal.