The defensins are a large family of small, cationic, cysteine- and arginine-rich antimicrobial peptides. They are divided into five groups according to the spacing pattern of cysteines: plant, invertebrate, α-, β-, and θ-defensins. The latter three are mostly found in mammals. a-defensins are proteins found in neutrophils and intestinal epithelia. Human neutrophil peptides (HNP) 1-3 are microbicidal and cytotoxic defensins derived from a 94-amino acid prepro HNP1-94, co-translationally proteolyzed to proHNP20-94, then converted by removal of the anionic propiece to mature HNP65-94 (HNP-1 and -3) and HNP66-94 (HNP-2). HNP 1-4 make up approximately 5% of the total cellular protein of neutrophils.
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