Defensin

Defensin
Example defensins with alpha helix in red, beta strands in blue, disulphide bonds in yellow (PDB: 1MR4, 2KOZ, 1FJN, 2LXZ, 1IJV, 2RNG​)
Identifiers
SymbolDefensin
Pfam clanCL0075
OPM superfamily54
OPM protein6cs9

Defensins are small cysteine-rich cationic proteins across cellular life, including vertebrate[1] and invertebrate[2] animals, plants,[3][4] and fungi.[5] They are host defense peptides, with members displaying either direct antimicrobial activity, immune signaling activities, or both. They are variously active against bacteria, fungi and many enveloped and nonenveloped viruses. They are typically 18-45 amino acids in length, with three or four highly conserved disulphide bonds.

In animals, they are produced by cells of the innate immune system and epithelial cells, whereas in plants and fungi they are produced by a wide variety of tissues. An organism usually produces many different defensins, some of which are stored inside the cells (e.g. in neutrophil granulocytes to kill phagocytosed bacteria), and others are secreted into the extracellular medium. For those that directly kill microbes, their mechanism of action varies from disruption of the microbial cell membrane to metabolic disruption.

  1. ^ Hazlett L, Wu M (January 2011). "Defensins in innate immunity". Cell and Tissue Research. 343 (1): 175–88. doi:10.1007/s00441-010-1022-4. PMID 20730446. S2CID 2234617.
  2. ^ Tassanakajon A, Somboonwiwat K, Amparyup P (February 2015). "Sequence diversity and evolution of antimicrobial peptides in invertebrates". Developmental and Comparative Immunology. Specific immunity in invertebrates. 48 (2): 324–41. doi:10.1016/j.dci.2014.05.020. PMID 24950415.
  3. ^ Thomma BP, Cammue BP, Thevissen K (December 2002). "Plant defensins". Planta. 216 (2): 193–202. Bibcode:2002Plant.216..193T. doi:10.1007/s00425-002-0902-6. PMID 12447532. S2CID 19356421.
  4. ^ Sathoff AE, Samac DA (May 2019). "Antibacterial Activity of Plant Defensins". Molecular Plant-Microbe Interactions. 32 (5): 507–514. doi:10.1094/mpmi-08-18-0229-cr. PMID 30501455.
  5. ^ Wu J, Gao B, Zhu S (August 2014). "The fungal defensin family enlarged". Pharmaceuticals. 7 (8): 866–80. doi:10.3390/ph7080866. PMC 4165938. PMID 25230677.