Invertebrate defensins are a family of cysteine-rich antimicrobial peptides, primarily active against Gram-positive bacteria. These defensins have been found in arthropods (insects, ticks, spiders and scorpions), in bivalve molluscs and in a fungus. These peptides range in length from 32 to 51 amino acids. There are six conserved cysteines all involved in intrachain disulfide bonds. A schematic representation of peptides from the invertebrate defensin family is shown below.

            +----------------------------+
            |                            |
         xxxCxxxxxxxxxxxxxxCxxxCxxxxxxxxxCxxxxxCxCxx
                           |   |               | |
                           +---|---------------+ |
                               +-----------------+

'C': conserved cysteine involved in a disulfide bond.

Some peptides known to belong to this family are listed below.

• Phormicin A and B from black blowfly (Phormia terranovae) [1].
• Royalisin from the royal jelly of honey bee [2].
• Sapecin, sapecin B and sapecin C from flesh fly (Sarcophaga peregrina) [3].
• Antibacterial peptides B and C from the beetle Zophobas atratus [4].
• Defensin from the larva of the dragonfly Aeschna cyanea [5].
• Defensin from Pyrrhocoris apterus [6].
• 4 Kd defensin from the scorpion Leiurus quinquestriatus hebraeus [7].
• Defensin heliomicin from the larva, tobacco budworm, of Heliothis virescens with potent anti-fungal activity [8].
• Defensins from mussels (Mytilus edulis and M. galloprovincialis).
• Defensin from oyster (Crassostrea virginica) [9].
• Plectasin from a saprophytic fungus (Pseudoplectania nigrella) [10].

We developed a profile that covers the whole structure of invertebrate defensins.