Cathelicidin-related antimicrobial peptides are a family of polypeptides found in lysosomes of macrophages and polymorphonuclear leukocytes (PMNs). Cathelicidins serve a critical role in mammalian innate immune defense against invasive bacterial infection.
Members of the cathelicidin family of antimicrobial polypeptides are characterized by a highly conserved region (cathelin domain) and a highly variable cathelicidin peptide domain.
Cathelicidin peptides have been isolated from many different species of mammals. Cathelicidins were originally found in neutrophils but have since been found in many other cells including epithelial cells and macrophages after activation by bacteria, viruses, fungi, or the hormone 1,25-D, which is the hormonally active form of vitamin D.
The cathelicidin family shares primary sequence homology with the cystatin family of cysteine proteinase inhibitors, although amino acid residues thought to be important in such protease inhibition are usually lacking.
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