CIQ-UP - Centro de Investigação em Química, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto , 4169-007 Porto, Portugal.
i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto , 4200-135 Porto, Portugal.
Langmuir. 2018 Feb 6;34(5):2158-2170. doi: 10.1021/acs.langmuir.7b03639. Epub 2018 Jan 22.
An understanding of the mechanism of action of antimicrobial peptides is fundamental to the development of new and more active antibiotics. In the present work, we use a wide range of techniques (SANS, SAXD, DSC, ITC, CD, and confocal and electron microscopy) in order to fully characterize the interaction of a cecropin A-melittin hybrid antimicrobial peptide, CA(1-7)M(2-9), of known antimicrobial activity, with a bacterial model membrane of POPE/POPG in an effort to unravel its mechanism of action. We found that CA(1-7)M(2-9) disrupts the vesicles, inducing membrane condensation and forming an onionlike structure of multilamellar stacks, held together by the intercalated peptides. SANS and SAXD revealed changes induced by the peptide in the lipid bilayer thickness and the bilayer stiffening in a tightly packed liquid-crystalline lamellar phase. The analysis of the observed abrupt changes in the repeat distance upon the phase transition to the gel state suggests the formation of an L phase. To the extent of our knowledge, this is the first time that the L phase is identified as part of the mechanism of action of antimicrobial peptides. The energetics of interaction depends on temperature, and ITC results indicate that CA(1-7)M(2-9) interacts with the outer leaflet. This further supports the idea of a surface interaction that leads to membrane condensation and not to pore formation. As a result, we propose that this peptide exerts its antimicrobial action against bacteria through extensive membrane disruption that leads to cell death.
了解抗菌肽的作用机制对于开发新的、更有效的抗生素至关重要。在本工作中，我们使用了广泛的技术（小角 X 射线散射、广角 X 射线散射、差示扫描量热法、等温热力学滴定、圆二色性、共聚焦和电子显微镜）来全面表征具有已知抗菌活性的抗菌肽 Cecropin A-Melit-tin 杂合肽 CA(1-7)M(2-9)与 POPE/POPG 细菌模型膜的相互作用，以揭示其作用机制。我们发现 CA(1-7)M(2-9)破坏了囊泡，诱导膜浓缩并形成洋葱状的多层堆叠结构，由插入的肽结合在一起。小角 X 射线散射和广角 X 射线散射揭示了肽在脂质双层厚度和双层变硬方面引起的变化，形成了紧密堆积的液晶层状相。对观察到的相变到凝胶态时重复距离的突然变化的分析表明形成了 L 相。据我们所知，这是首次将 L 相确定为抗菌肽作用机制的一部分。相互作用的热力学取决于温度，等温热力学滴定结果表明 CA(1-7)M(2-9)与外叶层相互作用。这进一步支持了表面相互作用的观点，导致膜浓缩而不是孔形成。因此，我们提出，这种肽通过广泛的膜破坏发挥其抗菌作用，导致细胞死亡。
