PROSITE documentation PDOC00244

Plant thionins signature

Thionins are small, basic, plant proteins generally toxic to animal cells [1]. They seem to exert their toxic effect at the level of the cell membrane but their exact function is not known. They consist of a polypeptide chain of forty five to fifty amino acids with three to four internal disulfide bonds. They are found in seeds but also in the cell wall of leaves [2]. Thionins are processed from larger precursor proteins [3]. Crambin [4], a hydrophobic plant seed protein, also belongs to this family. The pattern we developed to detect this family of proteins includes three of the six cysteine residues involved in disulfide bonds.

          +-----------------------------------+
          |+----------------------------+     |
          ||                            |     |
        xxCCxxxxxxxxxxxCxxxxxxxxxCxxxCxxCxxxxxCxxxxxxxx
          **************         |
                       |         |
                       +---------+

'C': conserved cysteine involved in a disulfide bond.
'*': position of the pattern.