Defensin

A defensin is a small cation protein found in animals and plants. They are host defence peptides. They work against bacteria, fungi and many viruses. 

Defensins have 18-45 amino acids including six to eight conserved cysteine residues."Conserved" means the sequence stays the same in almost all individuals in the population. Cells of the immune system have these peptides to help kill phagocytosed bacteria. Those cells include neutrophil granulocytes and almost all epithelial cells. Most defensins work by binding to the microbial cell membrane. Once there, they make tiny holes in the membrane which allow vital ions and nutrients to leak out.

 Related pages 
Host defence peptide
Lysozyme
innate immune system

 Notes 

Category:Proteins
Category:Immunology