These antimicrobial peptides were originally derived from the defense systems of insects, mammals, amphibians, etc., and they mainly include four categories:
1. cecropin was originally present in the immune lymph of Cecropiamoth, which is mainly found in other insects, and similar bactericidal peptides are also found in pig intestines. They are typically characterized by a strongly alkaline N-terminal region followed by a long hydrophobic fragment.
2. Xenopus antimicrobial peptides (magainin) are derived from the muscles and stomach of frogs. The structure of xenopus antimicrobial peptides was also found to be helical, especially in hydrophobic environments. The configuration of xenopus antipeptides in lipid layers was studied by N-labeled solid-phase NMR. Based on the chemical shift of acylamine resonance, the helices of xenopus antipeptides were parallel bilayer surfaces, and they could converge to form a 13mm cage with a periodic helical structure of 30mm.
3. defensin Defense peptides are derived from human polykaryotic neutrophil rabbit polymacrophages with complete nuclear lobule and intestinal cells of animals. A group of antimicrobial peptides similar to mammalian defense peptides were extracted from insects, called “insect defense peptides”. Unlike mammalian defense peptides, insect defense peptides are only active against Gram-positive bacteria. Even insect defense peptides contain six Cys residues, but the method of disulfide bonding to each other is different. The intramolecular disulfide bridge binding mode of antibacterial peptides extracted from Drosophila melanogast was similar to that of plant defense peptides. Under crystal conditions, defense peptides are presented as dimers.
4.Tachyplesin is derived from horseshoe crabs, called horseshoecrab. Configuration studies show that it adopts an antiparallel B-folding configuration (3-8 positions, 11-16 positions), in which β-angle is connected to each other (8-11 positions), and two disulfide bonds are generated between the 7 and 12 positions, and between the 3 and 16 positions. In this structure, the hydrophobic amino acid is located on one side of the plane, and the six cationic residues appear on the tail of the molecule, so the structure is also biophilic.
It follows that almost all antimicrobial peptides are cationic in nature, even though they vary in length and height; At the high end, whether in the form of alpha-helical or β-folding, bitropic structure is the common feature.
Post time: Apr-20-2023