Human Antimicrobial Peptides: Defensins, Cathelicidins and Histatins |
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Authors: | Kris De Smet Roland Contreras |
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Institution: | (1) Unit of Fundamental and Applied Molecular Biology, Department for Molecular Biomedical Research, Ghent University and VIB, Technologiepark 927, B-9052 Ghent, Belgium;(2) Present address: Flen Pharma NV, Drie Eikenstraat 661, B−2650 Edegem, Belgium |
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Abstract: | Antimicrobial peptides, which have been isolated from many bacteria, fungi, plants, invertebrates and vertebrates, are an
important component of the natural defenses of most living organisms. The isolated peptides are very heterogeneous in length,
sequence and structure, but most of them are small, cationic and amphipathic. These peptides exhibit broad-spectrum activity
against Gram-positive and Gram-negative bacteria, yeasts, fungi and enveloped viruses. A wide variety of human proteins and
peptides also have antimicrobial activity and play important roles in innate immunity. In this review we discuss three important
groups of human antimicrobial peptides. The defensins are cationic non-glycosylated peptides containing six cysteine residues
that form three intramolecular disulfide bridges, resulting in a triple-stranded β-sheet structure. In humans, two classes
of defensins can be found: α-defensins and β-defensins. The defensin-related HE2 isoforms will also be discussed. The second
group is the family of histatins, which are small, cationic, histidine-rich peptides present in human saliva. Histatins adopt
a random coil conformation in aqueous solvents and form α-helices in non-aqueous solvents. The third group comprises only
one antimicrobial peptide, the cathelicidin LL−37. This peptide is derived proteolytically from the C-terminal end of the human CAP18 protein. Just like the histatins, it adopts a largely random coil conformation in a hydrophilic
environment, and forms an α-helical structure in a hydrophobic environment. |
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Keywords: | antimicrobial peptides cathelicidin defensins histatins innate immunity |
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