Harnois I, Maget-Dana R, Ptak M
Centre de Biophysique Moléculaire, CNRS, Orléans, France.
Biochimie. 1989 Jan;71(1):111-6. doi: 10.1016/0300-9084(89)90140-5.
Iturin A, extracted from the culture media of Bacillus subtilis, is an antifungal lipopeptide, the peptide cycle of which includes a D-Tyr residue in position 2. The antibiotic strength of iturin A is related to a change in the permeability of the membrane cells which leads to a leakage of K+ from the intracellular medium. Methylation of the D-Tyr residue dramatically decreases the biological activity of iturin A. Using the intrinsic fluorescence of D-Tyr we have shown that both iturin A and O-methyl-tyrosine iturin A enter the lipid membranes. When dimyristoylphosphatidylcholine vesicles contain iturin A we observe a change in the order degree of the lipid phase and an increase in the transition temperature. The methylated derivative has no effect. Two model membranes have been used to study the permeability changes induced by iturin A and O-methyltyrosine iturin A. Studying ionic permeability we have found that the conductance of a planar lipid membrane increases very much less when the lipopeptide is methylated. On the other hand, the release of carboxyfluorescein trapped in lipid vesicles is less upon addition of O-methyltyrosine-iturin A. We conclude that the Tyr residue of the peptide cycle plays a role in determining the interactions of iturin A with lipid membrane.
iturin A是从枯草芽孢杆菌的培养基中提取的一种抗真菌脂肽，其肽环在第2位包含一个D-酪氨酸残基。iturin A的抗菌强度与膜细胞通透性的变化有关，这种变化会导致K+从细胞内介质中泄漏。D-酪氨酸残基的甲基化会显著降低iturin A的生物活性。利用D-酪氨酸的固有荧光，我们发现iturin A和O-甲基酪氨酸iturin A都能进入脂质膜。当二肉豆蔻酰磷脂酰胆碱囊泡含有iturin A时，我们观察到脂质相的有序度发生变化，转变温度升高。甲基化衍生物没有影响。我们使用了两种模型膜来研究iturin A和O-甲基酪氨酸iturin A引起的通透性变化。通过研究离子通透性，我们发现当脂肽甲基化时，平面脂质膜的电导增加得非常少。另一方面，加入O-甲基酪氨酸-iturin A后，被困在脂质囊泡中的羧基荧光素的释放减少。我们得出结论，肽环中的酪氨酸残基在决定iturin A与脂质膜的相互作用中起作用。
