Thennarasu Sathiah, Lee Dong-Kuk, Tan Anmin, Prasad Kari U, Ramamoorthy Ayyalusamy
Biophysics Research Division and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA.
Biochim Biophys Acta. 2005 Jun 1;1711(1):49-58. doi: 10.1016/j.bbamem.2005.02.010. Epub 2005 Mar 7.
Lipopeptide MSI-843 consisting of the nonstandard amino acid ornithine (Oct-OOLLOOLOOL-NH2) was designed with an objective towards generating non-lytic short antimicrobial peptides, which can have significant pharmaceutical applications. Octanoic acid was coupled to the N-terminus of the peptide to increase the overall hydrophobicity of the peptide. MSI-843 shows activity against bacteria and fungi at micromolar concentrations. It permeabilizes the outer membrane of Gram-negative bacterium and a model membrane mimicking bacterial inner membrane. Circular dichroism investigations demonstrate that the peptide adopts alpha-helical conformation upon binding to lipid membranes. Isothermal titration calorimetry studies suggest that the peptide binding to membranes results in exothermic heat of reaction, which arises from helix formation and membrane insertion of the peptide. 2H NMR of deuterated-POPC multilamellar vesicles shows the peptide-induced disorder in the hydrophobic core of bilayers. 31P NMR data indicate changes in the lipid head group orientation of POPC, POPG and Escherichia colitotal lipid bilayers upon peptide binding. Results from 31P NMR and dye leakage experiments suggest that the peptide selectively interacts with anionic bilayers at low concentrations (up to 5 mol%). Differential scanning calorimetry experiments on DiPOPE bilayers and 31P NMR data from E.coli total lipid multilamellar vesicles indicate that MSI-843 increases the fluid lamellar to inverted hexagonal phase transition temperature of bilayers by inducing positive curvature strain. Combination of all these data suggests the formation of a lipid-peptide complex resulting in a transient pore as a plausible mechanism for the membrane permeabilization and antimicrobial activity of the lipopeptide MSI-843.
由非标准氨基酸鸟氨酸（Oct - OOLLOOLOOL - NH2）组成的脂肽MSI - 843旨在生成非裂解性短抗菌肽，这类肽具有重要的药物应用价值。辛酸与该肽的N端偶联，以增加肽的整体疏水性。MSI - 843在微摩尔浓度下对细菌和真菌具有活性。它能使革兰氏阴性菌的外膜以及模拟细菌内膜的模型膜发生通透化。圆二色性研究表明，该肽在与脂质膜结合时会形成α - 螺旋构象。等温滴定量热法研究表明，该肽与膜的结合会导致反应放热，这源于肽的螺旋形成和膜插入。氘代 - POPC多层囊泡的2H NMR显示该肽会导致双层膜疏水核心出现无序状态。31P NMR数据表明，肽结合后，POPC、POPG和大肠杆菌总脂质双层膜的脂质头部基团取向发生了变化。31P NMR和染料泄漏实验结果表明，该肽在低浓度（高达5 mol%）时选择性地与阴离子双层相互作用。对DiPOPE双层膜进行的差示扫描量热法实验以及来自大肠杆菌总脂质多层囊泡的31P NMR数据表明，MSI - 843通过诱导正曲率应变提高了双层膜从流体层状相向反相六角相转变的温度。所有这些数据综合起来表明，形成脂质 - 肽复合物并产生瞬时孔道是脂肽MSI - 843膜通透化和抗菌活性的一种合理机制。
