Instituto de Física, Universidade de São Paulo, São Paulo, SP, 05080-900, Brazil.
Faculdade de Medicina, Universidade Federal de Goiás, Goiânia, GO, 74690-900, Brazil.
Eur Biophys J. 2022 Sep;51(6):493-502. doi: 10.1007/s00249-022-01615-y. Epub 2022 Aug 17.
The skin of amphibians is widely exploited as rich sources of membrane active peptides that differ in chain size, polypeptide net charge, secondary structure, target selectivity and toxicity. In this study, two small antimicrobial peptides, temporin-Ra and temporin-Rb, originally isolated from the skin of the European marsh frog (Rana ridibunda), described as active against pathogen bacteria and presenting low toxicity to eukaryotic cells were synthesized and had their physicochemical properties and mechanism of action investigated. The temporin peptides were examined in aqueous solution and in the presence of membrane models (lipid monolayers, micelles, lipid bilayers and vesicles). A combined approach of bioinformatics analyses, biological activity assays, surface pressure measurements, synchrotron radiation circular dichroism spectroscopy, and oriented circular dichroism spectroscopy were employed. Both peptides were able to adsorb at a lipid-air interface with a negative surface charge density, and efficiently disturb the lipid surface packing. A disorder-to-helix transition was observed on the secondary structure of both peptides when either in a non-polar environment or interacting with model membranes containing a negative net charge density. The binding of both temporin-Ra and temporin-Rb to membrane models is modulated by the presence of negatively charged lipids in the membrane. The amphipathic helix induced in temporin-Ra is oriented parallel to the membrane surface in negatively charged or in zwitterionic lipid bilayers, with no tendency for realignment after binding. Temporin-Rb, instead, assumes a β-sheet conformation when deposited into oriented stacked lipid bilayers. Due to their short size and simple composition, both peptides are quite attractive for the development of new classes of peptide-based anti-infective drugs.
两栖动物的皮肤是丰富的膜活性肽的来源，这些肽在链大小、多肽净电荷、二级结构、靶选择性和毒性方面有所不同。在这项研究中，两种小的抗菌肽，即来源于欧洲林蛙（Rana ridibunda）皮肤的天蚕素-Ra 和天蚕素-Rb，最初被描述为对病原体细菌有活性，并且对真核细胞毒性较低，被合成并研究了它们的理化性质和作用机制。这些天蚕素肽在水溶液中和膜模型（单层脂、胶束、双层脂和囊泡）中进行了检测。采用了生物信息学分析、生物活性测定、表面压力测量、同步辐射圆二色性光谱和定向圆二色性光谱相结合的方法。这两种肽都能够在带负电荷的脂-气界面上吸附，并有效地扰乱脂表面的堆积。当在非极性环境中或与含有负净电荷密度的模型膜相互作用时，两种肽的二级结构都观察到了从无序到螺旋的转变。带负电荷的脂质在膜中的存在调节了天蚕素-Ra 和天蚕素-Rb 与膜模型的结合。天蚕素-Ra 诱导的两亲性螺旋在带负电荷或两性离子脂双层中平行于膜表面排列，在结合后没有重新排列的趋势。而天蚕素-Rb 在定向堆叠的脂双层中则采取β-折叠构象。由于它们的小尺寸和简单组成，这两种肽都非常适合开发新型基于肽的抗感染药物。
