Peptaibols

Three structural characteristics define the group of polypeptides known as peptaibols:

A Short chain length, typically between 15 and 20 residues, although shorter ones are known.
A high proportion of the amino acid residues are non-standard. There is a particular propensity for Aminoisobutyric acid (Aib).
The chain has an alkyl N terminus (usually acetyl) and a hydroxy-amino acid at the C terminus.

Peptaibols generally exhibit antimicrobial activity and are referred to as antibiotic peptides. The main sources of the peptaibols known to date are fungii of the genre Trichoderma and Emericellopsis

The antomicrobial activity is thought to arise from the peptaibols' membrane activity and their ability to form pores in lipid membranes. The pores so formed are able to conduct ionic species; this conductance leads to the loss of osmotic balance and cell death.

Along with Aib, non standard residues which have been observed include Isovaline (Iva), Hydroxyproline (Hyp) and Ethylnorvaline (Etnor). Aminoisobutyric acid has a high tendency to form helices and this is borne out by the helical structures of the peptaibols.