Department of Chemistry, The City College of New York, New York, New York.
Department of Chemistry, The City College of New York, New York, New York; Graduate Programs in Chemistry, Biochemistry, and Physics, The Graduate Center, City University of New York, New York, New York.
Biophys J. 2018 Jun 19;114(12):2865-2874. doi: 10.1016/j.bpj.2018.05.006.
Melittin is a short cationic peptide that exerts cytolytic effects on bacterial and eukaryotic cells. Experiments suggest that in zwitterionic membranes, melittin forms transmembrane toroidal pores supported by four to eight peptides. A recently constructed melittin variant with a reduced cationic charge, MelP5, is active at 10-fold lower concentrations. In previous work, we performed molecular dynamics simulations on the microsecond timescale to examine the supramolecular pore structure of a melittin tetramer in zwitterionic and partially anionic membranes. We now extend that study to include the effects of peptide charge, initial orientation, and number of monomers on the pore formation and stabilization processes. Our results show that parallel transmembrane orientations of melittin and MelP5 are more consistent with experimental data. Whereas a MelP5 parallel hexamer forms a large stable pore during the 5-μs simulation time, a melittin hexamer and an octamer are not fully stable, with several monomers dissociating during the simulation time. Interaction-energy analysis shows that this difference in behavior between melittin and MelP5 is not due to stronger electrostatic repulsion between neighboring melittin peptides but to peptide-lipid interactions that disfavor the isolated MelP5 transmembrane monomer. The ability of melittin monomers to diffuse freely in the 1,2-dimyristoyl-SN-glycero-3-phosphocholine membrane leads to dynamic pores with varying molecularity.
蜂毒素是一种短的阳离子肽，对细菌和真核细胞具有细胞溶解作用。实验表明，在两性离子膜中，蜂毒素形成由四到八个肽支持的跨膜环形孔。最近构建的带弱电荷的蜂毒素变体 MelP5，其活性浓度低 10 倍。在以前的工作中，我们在微秒时间尺度上进行了分子动力学模拟，以研究两性离子和部分阴离子膜中四聚体蜂毒素的超分子孔结构。我们现在将该研究扩展到包括肽电荷、初始取向和单体数量对孔形成和稳定过程的影响。我们的结果表明，蜂毒素和 MelP5 的平行跨膜取向与实验数据更一致。虽然平行六聚体的 MelP5 在 5 微秒的模拟时间内形成一个大的稳定孔，但六聚体和八聚体的蜂毒素并不完全稳定，在模拟过程中有几个单体解离。相互作用能分析表明，蜂毒素和 MelP5 之间行为的这种差异不是由于相邻蜂毒素肽之间更强的静电排斥，而是由于肽-脂相互作用不利于孤立的 MelP5 跨膜单体。蜂毒素单体在 1,2-二肉豆蔻酰-SN-甘油-3-磷酸胆碱膜中自由扩散的能力导致具有不同分子数的动态孔。
