Plant defensin


Plant defensins are a family of small, cysteine-rich proteins found in plants that serve to defend them against parasites.
The following plant proteins belong to this family:
In their mature form, these proteins generally consist of about 45 to 50 amino-acid residues. As shown in the following schematic representation, these peptides contain eight conserved cysteines involved in disulfide bonds.
+-------------------------------------------+
| +-------------------+ |
| | | |

| | | |
+---|----------------+ |
+------------------+
'C': conserved cysteine involved in a disulfide bond.
The folded structure of Gamma-purothionin is characterised by a well-defined 3-stranded anti-parallel beta-sheet and a short alpha-helix. Three disulfide bridges are located in the hydrophobic core between the helix and sheet, forming a cysteine-stabilised alpha-helical motif. This structure differs from that of the plant alpha- and beta-thionins, but is analogous to scorpion toxins and insect defensins.

Databases

A database for antimicrobial peptides, including defensins is available: PhytAMP.

Subfamilies