Comparison of the Effects of Daptomycin on Bacterial and Model Membranes
Comparison of the Effects of Daptomycin on Bacterial and Model Membranes
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DOI：
10.1021/acs.biochem.8b00818
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发表时间：
2018-09-25
期刊：
影响因子：
2.9
通讯作者：
Huang, Huey W.
中科院分区：
文献类型：
--
作者：
Lee, Ming-Tao;Yang, Pei-Yin;Huang, Huey W.
达托霉素是一种磷脂酰甘油特异性、钙依赖的膜活性抗生素，已被批准用于治疗革兰氏阳性感染。最近对枯草芽孢杆菌的研究发现，达托霉素聚集在细菌膜的流体脂域中，膜结合与外周膜蛋白的错位和膜电位的去极化有关。特别是，这项研究否定了达托霉素离子通道的存在。我们在这里的目的是研究达托霉素如何与脂质双层相互作用，以了解在细菌膜上观察到的现象。我们使用带有离子泄漏指示器的吸入巨大囊泡进行了新型实验，比较了达托霉素和离子霉素，执行囊泡转移，并测量了达托霉素与液体相和凝胶相结合的双层和包括胆固醇在内的双层。我们的发现与细菌膜的观察结果完全一致。此外，只有当达托霉素在膜中的浓度超过一定阈值时，才会导致离子通过膜泄漏。达托霉素引起的离子渗漏是暂时性的。只有当达托霉素第一次与膜结合时，才会发生这种情况；之后，它们就不会引起离子泄漏。达托霉素的离子渗漏效应不能从一层膜转移到另一层膜。凝胶相与液体相相比，达托霉素的膜结合力降低。胆固醇也会削弱达托霉素的膜结合作用。膜浓度阈值和差异结合具有重要意义。这可能是达托霉素区分真核和原核细胞膜的原因之一。
Daptomycin is a phosphatidylglycerol specific, calcium-dependent membrane-active antibiotic that has been approved for the treatment of Gram-positive infections. A recent Bacillus subtilis study found that daptomycin clustered into fluid lipid domains of bacterial membranes and the membrane binding was correlated with dislocation of peripheral membrane proteins and depolarization of membrane potential. In particular, the study disproved the existence of daptomycin ion channels. Our purpose here is to study how daptomycin interacts with lipid bilayers to understand the observed phenomena on bacterial membranes. We performed new types of experiments using aspirated giant vesicles with an ion leakage indicator, making comparisons between daptomycin and ionomycin, performing vesicle vesicle transfers, and measuring daptomycin binding to fluid phase versus gel phase bilayers and bilayers including cholesterol. Our findings are entirely consistent with the observations for bacterial membranes. In addition, daptomycin is found to cause ion leakage through the membrane only if its concentration in the membrane is over a certain threshold. The ion leakage caused by daptomycin is transient. It occurs only when daptomycin binds the membrane for the first time; afterward, they cease to induce ion leakage. The ion leakage effect of daptomycin cannot be transferred from one membrane to another. The level of membrane binding of daptomycin is reduced in the gel phase versus the fluid phase. Cholesterol also weakens the membrane binding of daptomycin. The combination of membrane concentration threshold and differential binding is significant. This could be a reason why daptomycin discriminates between eukaryotic and prokaryotic cell membranes.