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Gamma thionin


Antifungal protein 1

Identifiers
Symbol	Gamma-thionin
Pfam	PF00304
InterPro	IPR008176
SCOP	1gps
OPM family	61
OPM protein	1jkz
Available PDB structures: 1gpt :1-47 1gps :1-47 1ti5A:28-73 1mr4A:26-72 1n4nA:26-72 1h3rA:28-72 1jkzA:1-46 1myn :27-70 1ayj :2-51 1bk8 :4-50

Gamma-thionins (also known as plant defensins) are small evolutionarily related proteins of plants that serves for their defense from parasites.

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The following plant proteins are belong to this family:

Gamma-thionins from Triticum aestivum (Wheat) endosperm (gamma-purothionins) and gamma-hordothionins from Hordeum vulgare(Barley) are toxic to animal cells and inhibit protein synthesis in cell free systems^[1].
A flower-specific thionin (FST) from Nicotiana tabacum (Common Tobacco)^[2].
Antifungal proteins (AFP) from the seeds of Brassicaceae species such as radish, mustard, turnip and Arabidopsis thaliana (Thale Cress)^[3].
Inhibitors of insect alpha-amylases from sorghum^[4].
Probable protease inhibitor P322 from Solanum tuberosum (Potato).
A germination-related protein from Vigna unguiculata (Cowpea)^[5].
Anther-specific protein SF18 from sunflower. SF18 is a protein that contains a gamma-thionin domain at its N-terminus and a proline-rich C-terminal domain.
Glycine max (Soybean) sulphur-rich protein SE60^[6].
Vicia faba (Broad bean) antibacterial peptides fabatin-1 and -2.

In their mature form, these proteins generally consist of about 45 to 50 amino-acid residues. As shown in the following schematic representation, these peptides contain eight conserved cysteines involved in disulphide bonds.

         +-------------------------------------------+
         |          +-------------------+            |
         |          |                   |            |
       xxCxxxxxxxxxxCxxxxxCxxxCxxxxxxxxxCxxxxxxCxCxxxC
                          |   |                | |
                          +---|----------------+ |

'C': conserved cysteine involved in a disulphide bond.

The folded structure of Gamma-purothionin is characterised by a well-defined 3-stranded anti-parallel beta-sheet and a short alpha-helix^[1]. Three disulphide bridges are located in the hydrophobic core between the helix and sheet, forming a cysteine-stabilised alpha-helical motif. This structure differs from that of the plant alpha- and beta-thionins, but is analogous to scorpion toxins and insect defensins.

References

^ ^a ^b Bruix M, Jime nez MA, Santoro J, Gonzalez C, Colilla FJ, Mendez E, Rico M (1993). "Solution structure of gamma 1-H and gamma 1-P thionins from barley and wheat endosperm determined by 1H-NMR: a structural motif common to toxic arthropod proteins". Biochemistry 32 (2): 715-724. PMID 8380707.
^ Gu Q, Kawata EE, Cheung AY, Morse MJ, Wu HM (1992). "A flower-specific cDNA encoding a novel thionin in tobacco". Mol. Gen. Genet. 234 (1): 89-96. PMID 1495489.
^ Osborn RW, Torrekens S, Vanderleyden J, Broekaert WF, Cammue BP, Terras FR, Van Leuven F (1993). "A new family of basic cysteine-rich plant antifungal proteins from Brassicaceae species". FEBS Lett. 316 (3): 233-240. PMID 8422949.
^ Richardson M, Bloch Jr C (1991). "A new family of small (5 kDa) protein inhibitors of insect alpha-amylases from seeds or sorghum (Sorghum bicolar (L) Moench) have sequence homologies with wheat gamma-purothionins". FEBS Lett. 279 (1): 101-104. PMID 1995329.
^ Ishibashi N, Yamauchi D, Minamikawa T (1990). "Stored mRNA in cotyledons of Vigna unguiculata seeds: nucleotide sequence of cloned cDNA for a stored mRNA and induction of its synthesis by precocious germination". Plant Mol. Biol. 15 (1): 59-64. PMID 2103443.
^ Choi Y, Choi YD, Lee JS (1993). "Nucleot ide sequence of a cDNA encoding a low molecular weight sulfur-rich protein in soybean seeds". Plant Physiol. 101 (2): 699-700. PMID 8278516.