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Plant thionin
Beta thionin.png
Wheat beta-purothionin. Alpha helices in red, beta sheets in blue, disulphide bridges in yellow. PDB: 1BHP
Symbol Thionin
Pfam PF00321
InterPro IPR001010
SCOP 1cnb
TCDB 1.C.44
OPM superfamily 149
OPM protein 2plh

Thionins (without an e) are a family of small proteins found solely in higher plants. Typically, a thionin consists of 45–48 amino acid residues. 6–8 of these are cysteine forming 3–4 disulfide bonds. Alpha- and beta- thionins are related to each other. The gamma thionins have a superficially similar structure but are an unrelated class of protein, now called plant defensins.


The proteins are toxic to animal cells, presumably attacking the cell membrane and rendering it permeable: this results in the inhibition of sugar uptake and allows potassium and phosphate ions, proteins, and nucleotides to leak from cells.[1] Thionins are mainly found in seeds where they may act as a defence against consumption by animals. A barley (Hordeum vulgare) leaf thionin that is highly toxic to plant pathogens and is involved in the mechanism of plant defence against microbial infections has also been identified.[2] The hydrophobic protein crambin from the Abyssinian kale (Crambe abyssinica) is also a member of the thionin family.[1] Some thionins have cytotoxic activity and they are therefore interesting in the development of new drugs against cancer with novel action mechanisms.[3] No thionin has yet been developed into an anti-cancer drug. Thionin is also a minor protein found in mustard (Brassica napus L.) seeds.[4]


A database for antimicrobial peptides, including thionins is available: PhytAMP.[5]

See also[edit]


  1. ^ a b Vernon LP, Evett GE, Zeikus RD, Gray WR (1985). "A toxic thionin from Pyrularia pubera: purification, properties, and amino acid sequence". Arch. Biochem. Biophys. 238 (1): 18–29. doi:10.1016/0003-9861(85)90136-5. PMID 3985614. 
  2. ^ Apel K, Andresen I, Becker W, Schluter K, Burges J, Parthier B (1992). "The identification of leaf thionin as one of the main jasmonate-induced proteins of barley (Hordeum vulgare)". Plant Mol. Biol. 19 (2): 193–204. doi:10.1007/BF00027341. PMID 1377959. 
  3. ^ Florack DE, Stiekema WJ (October 1994). "Thionins: properties, possible biological roles and mechanisms of action". Plant Mol. Biol. 26 (1): 25–37. doi:10.1007/BF00039517. PMID 7948874. 
  4. ^ Bérot S; Compoint JP; Larré C; Malabat C; Guéguen J. (2012). "Selective extraction, structural characterisation and antifungal activity assessment of napins from an industrial rapeseed meal". Food Chem. 134 (4): 2149–2155. doi:10.1016/j.jchromb.2004.08.001. PMID 7948874. 
  5. ^ "PhytAMP Database". ; Hammami R, Ben Hamida J, Vergoten G, Fliss I (January 2009). "PhytAMP: a database dedicated to antimicrobial plant peptides". Nucleic Acids Res. 37 (Database issue): D963–8. doi:10.1093/nar/gkn655. PMC 2686510Freely accessible. PMID 18836196.