Lipid A and anionic phospholipids

Lipid A is the highly conserved, hydrophobic anchor of lipopolysaccharide (LPS) located in the outer leaflet of the outer membrane of Gram-negative bacteria (Raetz & Whitfield, 2002). It serves as a critical structural component and acts as a potent endotoxin, triggering robust inflammatory responses through the TLR4/MD-2 complex in mammals (Park et al., 2009). Anionic phospholipids, such as phosphatidylglycerol and cardiolipin, are essential constituents of both the inner and outer bacterial membranes, providing a negative surface charge (Sohlenkamp & Geiger, 2016). These molecules are primary targets for cationic antimicrobial peptides and lipopeptide antibiotics like polymyxins (Trimble et al., 2016). Drugs targeting these lipids typically work by displacing stabilizing divalent cations, leading to membrane permeabilization, loss of cytoplasmic contents, and rapid bacterial cell death (Trimble et al., 2016). Because these lipids are fundamental to bacterial viability and are distinct from eukaryotic membrane lipids, they represent a vital target for treating multi-drug resistant Gram-negative infections, although clinical use is often limited by toxicity (Velkov et al., 2013). Resistance can emerge through enzymatic modifications of Lipid A, such as the addition of 4-amino-L-arabinose or phosphoethanolamine, which reduce the negative charge of the membrane and decrease drug affinity (Baron et al., 2016).

Other names

EndotoxinLipopolysaccharide anchorBacterial membrane lipidsAnionic bacterial lipidsLipid A moiety

Direct binding to negatively charged phosphate groups of Lipid A and anionic phospholipids, displacing stabilizing divalent cations (Mg2+, Ca2+), which leads to membrane disruption and cell death (Trimble et al., 2016).