Chemistry Institute, Faculty of Exact and Natural Sciences, University of Antioquia, Medellin, Colombia.
Laboratory of Advanced Analytical Techniques in Natural Products (LATNAP), Chemistry Department, Universidad de los Andes, Bogotá, Colombia; PhysCheMath Research Group, Chemistry Department, Universidad de América, Bogotá D.C., Colombia.
Biochim Biophys Acta Biomembr. 2024 Mar;1866(3):184288. doi: 10.1016/j.bbamem.2024.184288. Epub 2024 Jan 28.
Staphylococcus aureus is an opportunistic pathogen that is considered a global health threat. This microorganism can adapt to hostile conditions by regulating membrane lipid composition in response to external stress factors such as changes in pH and ionic strength. S. aureus synthesizes and incorporates in its membrane staphyloxanthin, a carotenoid providing protection against oxidative damage and antimicrobial agents. Staphyloxanthin is known to modulate the physical properties of the bacterial membranes due to the rigid diaponeurosporenoic group it contains. In this work, preparative thin layer chromatography and liquid chromatography mass spectrometry were used to purify staphyloxanthin from S. aureus and characterize its structure, identifying C15, C17 and C19 as the main fatty acids in this carotenoid. Changes in the biophysical properties of models of S. aureus membranes containing phosphatidylglycerol, cardiolipin, and staphyloxanthin were evaluated. Infrared spectroscopy shows that staphyloxanthin reduces the liquid-crystalline to gel phase transition temperature in the evaluated model systems. Interestingly, these shifts are not accompanied by strong changes in trans/gauche isomerization, indicating that chain conformation in the liquid-crystalline phase is not altered by staphyloxanthin. In contrast, headgroup spacing, measured by Laurdan GP fluorescence spectroscopy, and lipid core dynamics, measured by DPH fluorescence anisotropy, show significant shifts in the presence of staphyloxanthin. The combined results show that staphyloxanthin reduces lipid core dynamics and headgroup spacing without altering acyl chain conformations, therefore decoupling these normally correlated effects. We propose that the rigid diaponeurosporenoic group in staphyloxanthin and its positioning in the membrane is likely responsible for the results observed.
金黄色葡萄球菌是一种机会性病原体，被认为是全球健康威胁。这种微生物可以通过调节膜脂质组成来适应恶劣的环境条件，以响应外部应激因素，如 pH 值和离子强度的变化。金黄色葡萄球菌合成并将其膜中的番茄红素纳入其中，番茄红素提供了对氧化损伤和抗菌剂的保护。已知番茄红素通过其所含的刚性 diaponeurosporenoic 基团来调节细菌膜的物理性质。在这项工作中，制备性薄层色谱和液相色谱-质谱联用技术用于从金黄色葡萄球菌中纯化番茄红素，并对其结构进行了表征，确定 C15、C17 和 C19 为该类胡萝卜素中的主要脂肪酸。评估了含有磷脂酰甘油、心磷脂和番茄红素的金黄色葡萄球菌膜模型的生物物理性质变化。红外光谱表明，番茄红素降低了评估模型系统中从液晶相到凝胶相的转变温度。有趣的是，这些转变没有伴随着 trans/gauche 异构化的强烈变化，表明番茄红素不会改变液晶相中的链构象。相比之下，通过 Laurdan GP 荧光光谱测量的头部基团间隔和通过 DPH 荧光各向异性测量的脂质核心动力学，在存在番茄红素时显示出显著的变化。综合结果表明，番茄红素降低了脂质核心动力学和头部基团间隔，而不改变酰基链构象，因此解耦了这些通常相关的效应。我们提出，番茄红素中的刚性 diaponeurosporenoic 基团及其在膜中的定位可能是导致观察到的结果的原因。
