Beta defensin
| Beta defensin | |||||||||
|---|---|---|---|---|---|---|---|---|---|
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| Identifiers | |||||||||
| Symbol | Defensin_beta | ||||||||
| Pfam | PF00711 | ||||||||
| InterPro | IPR001855 | ||||||||
| SCOP | 1bnb | ||||||||
| SUPERFAMILY | 1bnb | ||||||||
| OPM superfamily | 56 | ||||||||
| OPM protein | 1ut3 | ||||||||
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| Available protein structures: | |
|---|---|
| Pfam | structures |
| PDB | RCSB PDB; PDBe; PDBj |
| PDBsum | structure summary |
Beta defensins are a family of mammalian defensins. The beta defensins are antimicrobial peptides implicated in the resistance of epithelial surfaces to microbial colonization.
Defensins are 2-6 kDa, cationic, microbicidal peptides active against many Gram-negative and Gram-positive bacteria, fungi, and enveloped viruses, containing three pairs of intramolecular disulfide bonds. On the basis of their size and pattern of disulfide bonding, mammalian defensins are classified into alpha, beta and theta categories. Every mammalian species explored thus far has beta-defensins. In cows, as many as 13 beta-defensins exist in neutrophils. However, in other species, beta-defensins are more often produced by epithelial cells lining various organs (e.g. the epidermis, bronchial tree and genitourinary tract.
Human, rabbit and guinea-pig beta-defensins, as well as human beta-defensin-2 (hBD2), induce the activation and degranulation of mast cells, resulting in the release of histamine and prostaglandin D2.
β-defensins are coding for genes which impact the function of the innate immune system. These genes are responsible for production of antimicrobial peptides found in white blood cells such as macrophages, granulocytes and NK-cells, β-defensins are also found in epithelial cells.Single-nucleotide polymorphisms (SNPs) are found in genes coding for β-defensins. The presences of SNPs are lower in the coding regions compared to non-coding regions. The appearance of SNPs in the coding region will highly likely affecting the resistance against infections through changes in the protein sequences which will give rise to different biological functions.
Receptors such as toll-like receptors (TLR) and nod-like receptors (NLR) will activate the immune system by binding of ligands such as lipopolysaccharides and peptidoglycan.Toll-like receptors are expressed in intestinal epithelial cells or antigen presenting cells (APCs) such as dendritic cells, B-lymphocytes and macrophages. When the receptors are activated a cascade reaction will take place and substances such as cytokines and antimicrobial peptides will be released.
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