Sepehri Aliasghar, PeBenito Leo, Pino-Angeles Almudena, Lazaridis Themis
Department of Chemistry & Biochemistry, The City College of New York, New York, New York.
Department of Chemistry & Biochemistry, The City College of New York, New York, New York; Graduate Program in Chemistry, The Graduate Center, City University of New York, New York, New York.
Biophys J. 2020 Apr 21;118(8):1901-1913. doi: 10.1016/j.bpj.2020.02.024. Epub 2020 Mar 3.
Pore formation by membrane-active peptides, naturally encountered in innate immunity and infection, could have important medical and technological applications. Recently, the well-studied lytic peptide melittin has formed the basis for the development of combinatorial libraries from which potent pore-forming peptides have been derived, optimized to work under different conditions. We investigate three such peptides, macrolittin70, which is most active at neutral pH; pHD15, which is active only at low pH; and MelP5_Δ6, which was rationally designed to be active at low pH but formed only small pores. There are three, six, and six acidic residues in macrolittin70, pHD15, and MelP5_Δ6, respectively. We perform multi-microsecond simulations in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) of hexamers of these peptides starting from transmembrane orientations at neutral pH (all residues at standard protonation), low pH (acidic residues and His protonated), and highly acidic environments in which C-termini are also protonated. Previous simulations of the parent peptides melittin and MelP5 in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) are repeated in POPC. We find that the most potent pore-forming peptides exhibit strong interpeptide interactions, including salt bridges, H-bonds, and polar interactions. Protonation of the C-terminus promotes helicity and pore size. The proximity of the peptides allows fewer lipid headgroups to line the pores than in previous simulations, making the pores intermediate between barrel stave and toroidal. Based on these structures and geometrical arguments, we attempt to rationalize the factors that under different conditions can increase or decrease pore stability and propose mutations that could be tested experimentally.
在天然免疫和感染过程中自然存在的膜活性肽形成孔道，可能具有重要的医学和技术应用。最近，经过充分研究的溶细胞肽蜂毒肽已成为组合文库开发的基础，从中衍生出了有效的成孔肽，并针对不同条件进行了优化。我们研究了三种这样的肽，即在中性pH下活性最强的大蜂毒肽70；仅在低pH下有活性的pHD15；以及经合理设计在低pH下有活性但仅形成小孔的MelP5_Δ6。大蜂毒肽70、pHD15和MelP5_Δ6分别有三个、六个和六个酸性残基。我们在1-棕榈酰-2-油酰-sn-甘油-3-磷酸胆碱（POPC）中对这些肽的六聚体进行了多微秒模拟，起始取向为中性pH（所有残基处于标准质子化状态）、低pH（酸性残基和组氨酸质子化）以及C末端也质子化的高酸性环境下的跨膜取向。在POPC中重复了之前在1,2-二肉豆蔻酰-sn-甘油-3-磷酸胆碱（DMPC）中对亲本肽蜂毒肽和MelP5的模拟。我们发现，最有效的成孔肽表现出强烈的肽间相互作用，包括盐桥、氢键和极性相互作用。C末端的质子化促进了螺旋度和孔径。与之前的模拟相比，肽之间的接近使得排列在孔道内的脂质头部基团更少，从而使孔道介于桶板状和环形之间。基于这些结构和几何参数，我们试图阐明在不同条件下可增加或降低孔道稳定性的因素，并提出可通过实验测试的突变。
