Maget-Dana R, Harnois I, Ptak M
Centre de Biophysique Moléculaire, C.N.R.S., Orléans, France.
Biochim Biophys Acta. 1989 Jun 6;981(2):309-14. doi: 10.1016/0005-2736(89)90042-4.
The miscibility and the interactions of the antifungal lipopeptide iturin A with lipids, DMPC and cholesterol, are studied in monolayers at the air/water interface and a comparison of the respective behaviour of iturin A and the biologically inactive methylated derivative MeTyr-iturin A is made. Each lipopeptide is miscible with anyone of the lipids. This behaviour is revealed by the dependence of the transition pressure upon composition and by deviations from the additivity rule of the mean molecular area. The thermodynamic properties of the mixed systems are studied by the method of Goodrich. The mixed monolayers are always more stable than the two separate components, subsequently there are interactions between the components. However, the excess free energy of mixing delta Gexm is positive for the iturin A/DMPC system which is an indication that the interactions between lipopeptide and lipid molecules are weaker than the interactions between the pure components themselves. This is compatible with the presence of self-associated lipopeptide molecules. However, delta Gexm is highly negative for the iturin A/cholesterol system giving evidence of the formation of a specific complex between iturin A and cholesterol which is not the case with the methylated derivative. These data are analysed in connection with previous results concerning the pore-forming properties of these lipopeptides and the lack of biological activity of MeTyr-iturin A.
在空气/水界面的单分子层中研究了抗真菌脂肽伊枯草菌素A与脂质二肉豆蔻酰磷脂酰胆碱（DMPC）和胆固醇的混溶性及相互作用，并对伊枯草菌素A和无生物活性的甲基化衍生物甲基酪氨酸 - 伊枯草菌素A的各自行为进行了比较。每种脂肽都能与任何一种脂质混溶。这种行为通过转变压力对组成的依赖性以及平均分子面积的加和规则偏差得以揭示。采用古德里奇方法研究了混合体系的热力学性质。混合单分子层总是比两种单独的组分更稳定，因此组分之间存在相互作用。然而，伊枯草菌素A/DMPC体系的混合过量自由能ΔGexm为正值，这表明脂肽与脂质分子之间的相互作用比纯组分自身之间的相互作用弱。这与自缔合脂肽分子的存在相符。然而，伊枯草菌素A/胆固醇体系的ΔGexm为高度负值，这证明伊枯草菌素A与胆固醇之间形成了特定复合物，而甲基化衍生物则不存在这种情况。结合先前关于这些脂肽的成孔性质以及甲基酪氨酸 - 伊枯草菌素A缺乏生物活性的结果对这些数据进行了分析。
