The following small plant proteins are evolutionary related:

• 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 | | | | +---|----------------+ | +------------------+

The folded structure of Gamma-purothionin is characterised by a well-defined 3-stranded anti-parallel beta-sheet and a short alpha-helix [7]. 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.

1. 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, 715-24
2. A flower-specific cDNA encoding a novel thionin in tobacco. Mol. Gen. Genet. 234, 89-96
3. A new family of basic cysteine-rich plant antifungal proteins from Brassicaceae species. FEBS Lett. 316, 233-40
4. 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, 101-4
5. 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, 59-64
6. Nucleotide sequence of a cDNA encoding a low molecular weight sulfur-rich protein in soybean seeds. Plant Physiol. 101, 699-700

The following small plant proteins are evolutionary related:

• Gamma-thionins from Show more...

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