Ön Ayse, Vejzovic Djenana, Jennings James, Parigger Lena, Cordfunke Robert A, Drijfhout Jan Wouter, Lohner Karl, Malanovic Nermina
Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria.
Department of Immunology, Leiden University Medical Center, 2333 Leiden, The Netherlands.
Antibiotics (Basel). 2023 Jul 8;12(7):1163. doi: 10.3390/antibiotics12071163.
OP-145 and SAAP-148, two 24-mer antimicrobial peptides derived from human cathelicidin LL-37, exhibit killing efficacy against both Gram-positive and Gram-negative bacteria at comparable peptide concentrations. However, when it comes to the killing activity against , the extent of membrane permeabilization does not align with the observed bactericidal activity. This is the case in living bacteria as well as in model membranes mimicking the cytoplasmic membrane (CM). In order to understand the killing activity of both peptides on a molecular basis, here we studied their mode of action, employing a combination of microbiological and biophysical techniques including differential scanning calorimetry (DSC), zeta potential measurements, and spectroscopic analyses. Various membrane dyes were utilized to monitor the impact of the peptides on bacterial and model membranes. Our findings unveiled distinct binding patterns of the peptides to the bacterial surface and differential permeabilization of the CM, depending on the smooth or rough/deep-rough lipopolysaccharide (LPS) phenotypes of strains. Interestingly, the antimicrobial activity and membrane depolarization were not significantly different in the different LPS phenotypes investigated, suggesting a general mechanism that is independent of LPS. Although the peptides exhibited limited permeabilization of membranes, DSC studies conducted on a mixture of synthetic phosphatidylglycerol/phosphatidylethanolamine/cardiolipin, which mimics the CM of Gram-negative bacteria, clearly demonstrated disruption of lipid chain packing. From these experiments, we conclude that depolarization of the CM and alterations in lipid packing plays a crucial role in the peptides' bactericidal activity.
OP-145和SAAP-148是两种源自人cathelicidin LL-37的24肽抗菌肽，在相当的肽浓度下对革兰氏阳性菌和革兰氏阴性菌均表现出杀伤效力。然而，在针对[具体对象未明确]的杀伤活性方面，膜通透性的程度与观察到的杀菌活性并不一致。在活细菌以及模拟细胞质膜（CM）的模型膜中都是如此。为了从分子层面理解这两种肽的杀伤活性，我们在此结合微生物学和生物物理技术，包括差示扫描量热法（DSC）、zeta电位测量和光谱分析，研究了它们的作用模式。使用了各种膜染料来监测肽对细菌膜和模型膜的影响。我们的研究结果揭示了肽与细菌表面的不同结合模式以及CM的不同通透性，这取决于菌株的光滑或粗糙/深粗糙脂多糖（LPS）表型。有趣的是，在所研究的不同LPS表型中，抗菌活性和膜去极化没有显著差异，这表明存在一种独立于LPS的一般机制。尽管肽对[具体对象未明确]膜的通透性有限，但对模拟革兰氏阴性菌CM的合成磷脂酰甘油/磷脂酰乙醇胺/心磷脂混合物进行的DSC研究清楚地表明了脂质链堆积的破坏。从这些实验中，我们得出结论，CM的去极化和脂质堆积的改变在肽的杀菌活性中起关键作用。
