Defensin

Function

Defensins (DEF) are small cationic defense proteins active against bacteria, fungi and viruses. DEF are found in cells of the immune system. DEF binds to microbial cell membrane forming pores and thus allowing outflow of essential nutrients thus killing them.^[1] For details on plant DEF see Plant defensin. Alpha-, beta- and theta-defensins are classified according to their invariant Cys-Cys spacings and the topology of the disulphide bridges.

• alpha defensins are antibiotic peptides produced in the Paneth cells of the small intestines defending against pathogens^[2].
• theta defensins are cyclic antibiotic peptides ^[3].

Relevance

There is increase in α-DEF in chronic inflammations and several cancers. DEF-mimetics are developed as antibiotics^[4].

Disease

Overexpression of α-defensin is seen in chronic inflammation, several cancers and in T-cells of schizophrenia patients^[5].

Structural highlights

DEF contains 6-8 conserved cysteine residues.

3D structures of defensin

Defensin 3D structures