Abdullah Swaleeha Jaan, Guan Jia Sheng, Mu Yuguang, Bhattacharjya Surajit
School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore.
Int J Mol Sci. 2024 Dec 24;26(1):51. doi: 10.3390/ijms26010051.
Host defense antimicrobial peptides (AMPs) are promising lead molecules with which to develop antibiotics against drug-resistant bacterial pathogens. Thanatin, an inducible antimicrobial peptide involved in the host defense of insects, is gaining considerable attention in the generation of novel classes of antibiotics. Thanatin or thanatin-based analog peptides are extremely potent in killing bacterial pathogens in the Enterobacteriaceae family, including drug-resistant strains of and . A single disulfide bond that covalently links two anti-parallel β-strands in thanatin could be pivotal to its selective antibacterial activity and mode of action. However, potential correlations of the disulfide covalent bond with structure, activity and target binding in thanatin peptides are currently unclear to. Here, we examined a 16-residue designed thanatin peptide, namely disulfide-bonded VF16QK, and its Cys to Ser substituted variant, VF16QK, to delineate their structure-activity relationships. Bacterial growth inhibitory activity was only detected for the disulfide-bonded VF16QK peptide. Mechanistically, both peptides vastly differ in their bacterial cell permeabilizations, atomic-resolution structures, interactions with the LPS-outer membrane and target periplasmic protein LptA binding. In particular, analysis of the 3-D structures of the two peptides revealed an altered folded conformation for the VF16QK peptide that was correlated with diminished LPS-outer membrane permeabilization and target interactions. Analysis of docked complexes of LPS-thanatin peptides indicated potential structural requirements and conformational adaptation for antimicrobial activity. Collectively, these observations contrast with those for the disulfide-bonded β-hairpin antimicrobial protegrin and tachyplesin peptides, where disulfide bonds are dispensable for activity. We surmise that the atomistic structures and associated molecular interactions presented in this work can be utilized to design novel thanatin-based antibiotics.
宿主防御抗菌肽（AMPs）是开发抗耐药性细菌病原体抗生素的有前景的先导分子。Thanatin是一种参与昆虫宿主防御的可诱导抗菌肽，在新型抗生素的研发中受到了广泛关注。Thanatin或基于Thanatin的类似肽在杀死肠杆菌科细菌病原体方面极具效力，包括耐药菌株。Thanatin中一个将两条反平行β链共价连接的二硫键可能对其选择性抗菌活性和作用方式至关重要。然而，目前尚不清楚Thanatin肽中二硫键与结构、活性和靶点结合之间的潜在关联。在此，我们研究了一种16个残基的设计Thanatin肽，即二硫键连接的VF16QK及其半胱氨酸到丝氨酸取代变体VF16QK，以阐明它们的构效关系。仅检测到二硫键连接的VF16QK肽具有细菌生长抑制活性。从机制上讲，这两种肽在细菌细胞通透性、原子分辨率结构、与脂多糖-外膜的相互作用以及与靶周质蛋白LptA结合方面有很大差异。特别是，对这两种肽的三维结构分析揭示了VF16QK肽折叠构象的改变，这与脂多糖-外膜通透性降低和靶点相互作用相关。脂多糖-Thnatin肽对接复合物的分析表明了抗菌活性的潜在结构要求和构象适应性。总的来说，这些观察结果与二硫键连接的β-发夹抗菌肽和鲎素肽的观察结果形成对比，在后者中，二硫键对活性是可有可无的。我们推测，这项工作中呈现的原子结构和相关分子相互作用可用于设计新型的基于Thanatin的抗生素。
