Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055,United States.
Biochemistry. 2010 Dec 21;49(50):10595-605. doi: 10.1021/bi101394r. Epub 2010 Nov 23.
In a minimalist design approach, a synthetic peptide MSI-367 [(KFAKKFA)(3)-NH(2)] was designed and synthesized with the objective of generating cell-selective nonlytic peptides, which have a significant bearing on cell targeting. The peptide exhibited potent activity against both bacteria and fungi, but no toxicity to human cells at micromolar concentrations. Bacterial versus human cell membrane selectivity of the peptide was determined via membrane permeabilization assays. Circular dichroism investigations revealed the intrinsic helix propensity of the peptide, β-turn structure in aqueous buffer and extended and turn conformations upon binding to lipid vesicles. Differential scanning calorimetry experiments with 1,2-dipalmitoleoyl-sn-glycero-3-phosphatidylethanolamine bilayers indicated the induction of positive curvature strain and repression of the fluid lamellar to inverted hexagonal phase transition by MSI-367. Results of isothermal titration calorimetry (ITC) experiments suggested the possibility of formation of specific lipid-peptide complexes leading to aggregation. (2)H nuclear magnetic resonance (NMR) of deuterated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) multilamellar vesicles confirmed the limited effect of the membrane-embedded peptide at the lipid-water interface. (31)P NMR data indicated changes in the lipid headgroup orientation of POPC, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol, and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylethanolamine lipid bilayers upon peptide binding. Membrane-embedded and membrane-inserted states of the peptide were observed via sum frequency generation vibrational spectroscopy. Circular dichroism, ITC, and (31)P NMR data for Escherichia coli lipids agree with the hypothesis that strong electrostatic lipid-peptide interactions embrace the peptide at the lipid-water interface and provide the basis for bacterial cell selectivity.
在一种极简主义设计方法中，设计并合成了一种合成肽 MSI-367[（KFAKKFA）（3）-NH（2）]，旨在产生对细胞具有靶向作用的细胞选择性非溶细胞肽。该肽对细菌和真菌均表现出强大的活性，但在微摩尔浓度下对人体细胞没有毒性。通过膜通透性测定来确定肽对细菌与人类细胞膜的选择性。圆二色性研究表明该肽具有内在的螺旋倾向，在水缓冲液中具有β-转角结构，并且在与脂质体结合时具有延伸和转角构象。用 1,2-二棕榈酰-sn-甘油-3-磷酸乙醇胺双层进行差示扫描量热法实验表明，MSI-367 诱导正曲率应变并抑制从流体层状到反相六方相的转变。等温滴定量热法（ITC）实验结果表明，可能形成特定的脂质-肽复合物导致聚集。（2）H 核磁共振（NMR）对氘化 1-棕榈酰-2-油酰-sn-甘油-3-磷酸胆碱（POPC）多层囊泡的研究证实了嵌入膜中的肽在脂质-水界面处的有限作用。（31）P NMR 数据表明，POPC、1-棕榈酰-2-油酰-sn-甘油-3-磷酸甘油和 1-棕榈酰-2-油酰-sn-甘油-3-磷酸乙醇胺脂质双层的脂质头部基团取向发生变化。通过和频产生振动光谱观察到肽的膜嵌入和膜插入状态。圆二色性、ITC 和（31）P NMR 数据表明，大肠杆菌脂质与强静电脂质-肽相互作用的假设一致，这些相互作用在脂质-水界面处包裹肽，并为细菌细胞选择性提供了基础。
