Cathelicidin

4EYC, 2FBS, 2FBU, 2FCG, 2K6O, 2LMF82012796ENSG00000164047ENSMUSG00000038357P49913P51437NM_004345NM_009921NP_004336NP_034051Cathelicidin-related antimicrobial peptides are a family of polypeptides primarily stored in the lysosomes of macrophages and polymorphonuclear leukocytes (PMNs). Cathelicidins serve a critical role in mammalian innate immune defense against invasive bacterial infection. The cathelicidin family of peptides are classified as antimicrobial peptides (AMPs). The AMP family also includes the defensins. Whilst the defensins share common structural features, cathelicidin-related peptides are highly heterogeneous. In humans, its precursor is encoded by the gene CAMP, which is cleaved into the active form LL-37. Cathelicidin-related antimicrobial peptides are a family of polypeptides primarily stored in the lysosomes of macrophages and polymorphonuclear leukocytes (PMNs). Cathelicidins serve a critical role in mammalian innate immune defense against invasive bacterial infection. The cathelicidin family of peptides are classified as antimicrobial peptides (AMPs). The AMP family also includes the defensins. Whilst the defensins share common structural features, cathelicidin-related peptides are highly heterogeneous. In humans, its precursor is encoded by the gene CAMP, which is cleaved into the active form LL-37. 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 general rule of the mechanism triggering cathelicidin action, like that of other antimicrobial peptides, involves the disintegration (damaging and puncturing) of cell membranes of organisms toward which the peptide is active. Cathelicidin rapidly destroys the lipoprotein membranes of microbes enveloped in phagosomes after fusion with lysosomes in macrophages. Cathelicidins range in size from 12 to 80 amino acid residues and have a wide range of structures. Most cathelicidins are linear peptides with 23-37 amino acid residues, and fold into amphipathic α-helices. Additionally cathelicidins may also be small-sized molecules (12-18 residues) with beta-hairpin structures, stabilized by one or two disulphide bonds. Even larger cathelicidin peptides (39-80 amino acid residues) are also present. These larger cathelicidins display repetitive proline motifs forming extended polyproline-type structures. 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.