Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, UK.
Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester M13 9PL, UK.
ACS Appl Mater Interfaces. 2021 Apr 14;13(14):16062-16074. doi: 10.1021/acsami.1c01643. Epub 2021 Apr 2.
Gram-negative bacteria are covered by both an inner cytoplasmic membrane (IM) and an outer membrane (OM). Antimicrobial peptides (AMPs) must first permeate through the OM and cell wall before attacking the IM to cause cytoplasmic leakage and kill the bacteria. The bacterial OM is an asymmetric bilayer with the outer leaflet primarily composed of lipopolysaccharides (LPSs) and the inner leaflet composed of phospholipids (PLs). Two cationic α-helical AMPs were designed to target Gram-negative bacteria, a full peptide G(IIKK)I-NH (G), and a hydrophobic lipopeptide C-G(IIKK)I-NH (CG, with C denoting the octanoyl chain). LPS dominates OM functions as the first line of defense against antibiotics, thereby reducing drug susceptibility. This work explores how the two AMPs interact with LPS through several carefully chosen OM models that facilitated measurements from solid-state nuclear magnetic resonance (ss-NMR), small-angle neutron scattering (SANS), and neutron reflectivity (NR). The results revealed that G molecules bound preferably to the LPS head region and functioned as bridge molecules to reassemble the dislocated lipids into bilayer stacks. In contrast, CG lipopeptides could quickly penetrate into the central region of the OM to cause direct removal of some membrane lipids. Different structural disruptions implicated different antimicrobial efficacies from these AMPs. The demonstration of the structural features underlying different susceptibilities of the OM to AMPs offers a useful route for the future development of strain-specific AMPs against antimicrobial-resistant pathogens.
革兰氏阴性菌的外膜（OM）和细胞质膜（IM）双层结构共同包裹着它们。抗菌肽（AMPs）必须先穿透 OM 和细胞壁，才能攻击 IM，导致细胞质泄漏并杀死细菌。细菌的 OM 是一个不对称的双层结构，外层主要由脂多糖（LPSs）组成，内层由磷脂（PLs）组成。为了靶向革兰氏阴性菌，设计了两种阳离子α-螺旋 AMP，一种是全长肽 G(IIKK)I-NH（G），另一种是疏水性脂肽 C-G(IIKK)I-NH（CG，其中 C 表示辛酰链）。LPS 作为抗生素的第一道防线，在 OM 中发挥着重要的作用，从而降低了药物的敏感性。本研究通过几种精心选择的 OM 模型，利用固态核磁共振（ss-NMR）、小角中子散射（SANS）和中子反射率（NR）进行测量，探讨了这两种 AMP 与 LPS 的相互作用方式。结果表明，G 分子优先与 LPS 的头部区域结合，并作为桥联分子将错位的脂质重新组装成双层堆叠。相比之下，CG 脂肽可以快速穿透 OM 的中心区域，直接去除一些膜脂质。不同的结构破坏方式暗示了这些 AMP 具有不同的抗菌功效。这些研究结果揭示了 OM 对 AMP 敏感性的结构特征，为未来针对抗药性病原体的特定菌株抗菌肽的开发提供了一条有用的途径。
