InterPro

The precursor sequences of a number of antimicrobial peptides secreted by neutrophils (polymorphonuclear leukocytes) upon activation have been found to be evolutionarily related and are collectively known as cathelicidins [PMID: 7589491].

Structurally, these proteins consist of three domains: a signal sequence, a conserved region of about 100 residues that contains four cysteines involved in two disulphide bonds, and a highly divergent C-terminal section of variable size. It is in this C-terminal section that the antibacterial peptides are found; they are proteolytically processed from their precursor by enzymes such as elastase. This structure is shown in the following schematic representation:

   +---+--------------------------------+--------------------+
   |Sig| Propeptide     C  C  C  C      | Antibacterial pep. |
   +---+----------------|--|--|--|------+--------------------+
                        |  |  |  |
                        +--+  +--+

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