This family of extracellular proteins is involved in stopping the formation of ice crystals at low temperatures. The proteins are composed of a 12 residue repeat that forms a structural repeat. The structure of the repeats is a beta helix [1]. Each repeat contains two cys residues that form a disulphide bridge.

1: Cold survival in freeze-intolerant insects: the structure and function of beta-helical antifreeze proteins. Graether SP, Sykes BD; Eur J Biochem. 2004;271:3285-3296. PMID:15291806