金黄色葡萄球菌,一种对多种药物有抗药性的细菌,是全世界疾病和死亡的重要原因。抗菌肽(AMPs)提供了一种出色的潜在策略来应对这种威胁。最近,我们表征了青蛙皮AMPesculentin-1a的衍生物,Esc(1-21)(1)具有针对革兰氏阴性细菌的有效活性,但针对革兰氏阳性菌株的功效较差。在这项研究中,通过用α-氨基异丁酸(Aib)代替Gly8设计了肽1的三个类似物,Pro,和dPro(分别为2-4)。肽2中的单取代Gly8→Aib8使其对革兰氏阳性细菌菌株的浮游形式具有活性,尤其是金黄色葡萄球菌,包括多重耐药的临床分离株,具有改进的生物稳定性,而不导致对哺乳动物细胞的细胞毒性。此外,肽2对金黄色葡萄球菌的参考和临床分离株显示出比肽1更高的抗生物膜活性。肽2还能够诱导快速的细菌杀灭,暗示了一种膜扰动的作用机制。对最具活性的肽2的结构分析证明,肽2的生物活性提高是生物稳定性较高的组合的结果,较高的α螺旋含量,以及降低膜流动性和采用扭曲螺旋的能力,弯曲对应的Aib8。总的来说,这项研究表明,战略性的单氨基酸取代足以扩大原始肽1的活性谱,并改善其用于治疗目的的生物学特性,从而为新型广谱抗感染药的开发铺平了道路。
Staphylococcus aureus, a bacterium resistant to multiple drugs, is a significant cause of illness and death worldwide. Antimicrobial peptides (AMPs) provide an excellent potential strategy to cope with this threat. Recently, we characterized a derivative of the frog-skin AMP esculentin-1a, Esc(1-21) (1) that is endowed with potent activity against Gram-negative bacteria but poor efficacy against Gram-positive strains. In this study, three analogues of peptide 1 were designed by replacing Gly8 with α-aminoisobutyric acid (Aib), Pro, and dPro (2-4, respectively). The single substitution Gly8 → Aib8 in peptide 2 makes it active against the planktonic form of Gram-positive bacterial strains, especially Staphylococcus aureus, including multidrug-resistant clinical isolates, with an improved biostability without resulting in cytotoxicity to mammalian cells. Moreover, peptide 2 showed a higher antibiofilm activity than peptide 1 against both reference and clinical isolates of S. aureus. Peptide 2 was also able to induce rapid bacterial killing, suggesting a membrane-perturbing mechanism of action. Structural analysis of the most active peptide 2 evidenced that the improved biological activity of peptide 2 is the consequence of a combination of higher biostability, higher α helical content, and ability to reduce membrane fluidity and to adopt a distorted helix, bent in correspondence of Aib8. Overall, this study has shown how a strategic single amino acid substitution is sufficient to enlarge the spectrum of activity of the original peptide 1, and improve its biological properties for therapeutic purposes, thus paving the way to optimize AMPs for the development of new broad-spectrum anti-infective agents.