Fig. 3.

Antimicrobial mechanisms of defensin. a The cell membrane structure of G⁻ and G⁺ bacteria. b Defensins accumulate on the cell membrane before destroying it. c–e Illustrations of the various modes of defensins-mediated cell killing, including the barrel-stave model, the toroidal pore model and the carpet model. f The structure Lipid II; g Cell wall biosynthesis begins in the cytoplasm where UDP-MurNAc-pentapeptide is formed. This soluble precursor is then linked to the membrane carrier bactoprenolphosphate (C₅₅P) by MraY, yielding Lipid I (reaction I). MurG subsequently adds GlcNAc to form Lipid II (reaction II). After the formation of the interpeptide bridge (as seen in reaction III), the monomeric peptidoglycan unit undergoes translocation across the cytoplasmic membrane for incorporation into the cell wall (reaction III). It is noteworthy that this interpeptide bridge formation is limited to some Gram-positive bacteria, as highlighted by research.³⁸ Note: To better demonstrate the crosstalk mechanism of defensins in regulating immune homeostasis, the intestine containing PCs and mucosal structures was used as the background of the regulatory network