2H-NMR and MD Simulations Reveal Membrane-Bound Conformation of Magainin 2 and Its Synergy with PGLa.
2H-NMR and MD Simulations Reveal Membrane-Bound Conformation of Magainin 2 and Its Synergy with PGLa.
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DOI：
10.1016/j.bpj.2016.10.012
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发表时间：
2016-11
影响因子：
3.4
通讯作者：
E. Strandberg;D. Horn;S. Reißer;Jonathan Zerweck;P. Wadhwani;A. Ulrich
中科院分区：
文献类型：
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作者：
E. Strandberg;D. Horn;S. Reißer;Jonathan Zerweck;P. Wadhwani;A. Ulrich
magin 2 （MAG2）和PGLa是在非洲非洲爪蟾皮肤中发现的两种α-螺旋抗菌肽。它们通过渗透细菌膜而起作用，并表现出典型的协同作用。在这里，我们通过对ala -d3标记的肽进行2h - nmr，确定了定向脂质双层中MAG2的详细分子定位和动力学行为，从而产生了标签的定向依赖的四极性分裂。在1,2-二肉豆蔻酰基-sn-甘油-3-磷脂酰胆碱(DMPC)/1,2-二肉豆蔻酰基-sn-甘油-3-磷脂酰甘油（DMPG）和1-棕榈酰基-2-油基-sn-甘油-3-磷脂酰胆碱(POPC)/1-棕榈酰基-2-油基-sn-甘油-3-磷脂酰甘油（POPG）中，发现两亲性的MAG2螺旋平躺在膜表面，倾斜角度接近90°。这种取向与在DMPC和DMPC/DMPG中进行的MAG2的全原子分子动力学模拟非常吻合。在等摩尔量的PGLa存在下，核磁共振分析表明，MAG2发生了120°的倾斜，其方位旋转角度也发生了变化。由于发现这种相互作用发生在肽本身不与自身类型相互作用的浓度范围内，我们提出MAG2与PGLa形成稳定的异源二聚体。鉴于已知复合物中的PGLa分子被翻转成完全直立的方向，螺旋倾斜接近180°，它们必须构成实际的跨膜孔。因此，我们认为斜倾斜的MAG2肽的c端上的两个负电荷中和了直立的PGLa螺旋上的一些阳离子基团。这将稳定PGLa组装成环形孔，整体电荷密度降低，这可以解释协同作用的机制。
Magainin 2 (MAG2) and PGLa are twoα-helical antimicrobial peptides found in the skin of the African frogXenopus laevis. They act by permeabilizing bacterial membranes and exhibit an exemplary synergism. Here, we determined the detailed molecular alignment and dynamical behavior of MAG2 in oriented lipid bilayers by using2H-NMR on Ala-d3-labeled peptides, which yielded orientation-dependent quadrupolar splittings of the labels. The amphiphilic MAG2 helix was found to lie flat on the membrane surface in 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC)/1,2-dimyristoyl-sn-glycero-3-phosphatidylglycerol (DMPG) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol (POPG), as expected, with a tilt angle close to 90°. This orientation fits well with all-atom molecular-dynamics simulations of MAG2 performed in DMPC and DMPC/DMPG. In the presence of an equimolar amount of PGLa, the NMR analysis showed that MAG2 becames tilted at an angle of 120°, and its azimuthal rotation angle also changes. Since this interaction was found to occur in a concentration range where the peptides per se do not interact with their own type, we propose that MAG2 forms a stable heterodimer with PGLa. Given that the PGLa molecules in the complex are known to be flipped into a fully upright orientation, with a helix tilt close to 180°, they must make up the actual transmembrane pore. We thus suggest that the two negative charges on the C-terminus of the obliquely tilted MAG2 peptides neutralize some of the cationic groups on the upright PGLa helices. This would stabilize the assembly of PGLa into a toroidal pore with an overall reduced charge density, which could explain the mechanism of synergy.