Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai, China.
Oak Ridge National Laboratory, Oak Ridge, Tennessee.
Biophys J. 2012 Aug 8;103(3):472-482. doi: 10.1016/j.bpj.2012.06.040.
The membrane-active antimicrobial peptide PGLa from Xenopus laevis is known from solid-state (2)H-, (15)N-, and (19)F-NMR spectroscopy to occupy two distinct α-helical surface adsorbed states in membranes: a surface-bound S-state with a tilt angle of ~95° at low peptide/lipid molar ratio (P/L = 1:200), and an obliquely tilted T-state with a tilt angle of 127° at higher peptide concentration (P/L = 1:50). Using a rapid molecular-dynamics insertion protocol in combination with microsecond-scale simulation, we have characterized the structure of both states in detail. As expected, the amphiphilic peptide resides horizontally on the membrane surface in a monomeric form at a low P/L, whereas the T-state is seen in the simulations to be a symmetric antiparallel dimer, with close contacts between small glycine and alanine residues at the interface. The computed tilt angles and azimuthal rotations, as well as the quadrupolar splittings predicted from the simulations agree with the experimental NMR data. The simulations reveal many structural details previously inaccessible, such as the immersion depth of the peptide in the membrane and the packing of the dimerization interface. The study highlights the ability and limitations of current state-of-the-art multimicrosecond all-atom simulations of membrane-active peptides to complement experimental data from solid-state NMR.
来自非洲爪蟾的膜活性抗菌肽 PGLa 从固态 (2)H、(15)N 和 (19)F-NMR 光谱中可知，它在膜中占据两种不同的α-螺旋表面吸附状态：低肽/脂摩尔比（P/L=1:200）时，倾斜角约为 95°的表面结合 S 态，以及较高肽浓度（P/L=1:50）时，倾斜角为 127°的倾斜 T 态。使用快速分子动力学插入协议与微秒级模拟相结合，我们详细地描述了这两种状态的结构。如预期的那样，在低 P/L 下，两亲肽以单体形式水平位于膜表面上，而在模拟中，T 态被视为对称的反平行二聚体，界面处的小甘氨酸和丙氨酸残基之间存在紧密接触。模拟预测的倾斜角和方位旋转以及四极分裂与实验 NMR 数据一致。模拟揭示了许多以前无法获得的结构细节，例如肽在膜中的浸深和二聚化界面的堆积。该研究强调了当前最先进的多微秒全原子模拟膜活性肽的能力和局限性，以补充固态 NMR 的实验数据。
