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Thionin

Field	Value
Symbol	Thionin
Name	Plant thionin
image	Beta thionin.png
caption	Wheat beta-purothionin. Alpha helices in red, beta sheets in blue, disulphide bridges in yellow.
Pfam	PF00321
InterPro	IPR001010
PROSITE	PDOC00244
SCOP	1cnb
TCDB	1.C.44
OPM family	140
OPM protein	2plh
PDB	1BHP

Thionins 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. They include phoratoxins and viscotoxins.

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.

Activity

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. 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. The hydrophobic protein crambin from the Abyssinian kale (Crambe abyssinica) is also a member of the thionin family. Some thionins have cytotoxic activity and they are therefore interesting in the development of new drugs against cancer with novel action mechanisms. No thionin has yet been developed into an anti-cancer drug. Thionin is also a minor protein found in mustard (Brassica napus L.) seeds.

Databases

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

References

(1985). "A toxic thionin from Pyrularia pubera: purification, properties, and amino acid sequence". Arch. Biochem. Biophys..
(1992). "The identification of leaf thionin as one of the main jasmonate-induced proteins of barley (Hordeum vulgare)". Plant Mol. Biol..
(October 1994). "Thionins: properties, possible biological roles and mechanisms of action". Plant Mol. Biol..
(2005). "Large scale purification of rapeseed proteins (Brassica napus L.)". Journal of Chromatography B.
(January 2009). "PhytAMP Database". Nucleic Acids Res..

Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

peripheral-membrane-proteins plant-toxins antimicrobial-peptides

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