Thionins: Plant peptides that modify membrane permeability in cultured mammalian cells

Journal/Book: Eur-J-Biochem 1981 May, VOL: 116 (1), P: 185-9, ISSN: 0014-2956.. 1981;

Abstract: Thionins, which are high-sulphur polypeptides present in the endospermof wheat and related species, have ben found to prevent growth and toinhibit macromolecular synthesis in cultured mammalian cells. Babyhamster kidney (BHK) cells were markedly more sensitive to thionins thanthe other cell lines tested (monkey CV1, mouse L, human HeLa). A thioninconcentration of 5 microgram/ml (1 microM) completely blockedtranslation in BHK cells. It was later found that omission of bothcalcium and magnesium ions from the medium strongly enhanced theinhibitory effects of thionins (BHK cells, 80% inhibition, 0.5microgram/ml). Several lines of evidence indicate that thionins mightact at the membrane level. Indeed, both the 86Rb+ content and thenucleotide pool of BHK cells were drastically decreased at thioninconcentrations that inhibited translation. In addition, thioninconcentrations that did not affect macromolecular synthesis in thesecells, allowed inhibition of translation by antibiotics, such ashygromycin B, that are not able to cross the cell plasma membrane bythemselves. Our results suggest that the inhibition of protein, RNA andDNA synthesis in BHK cells might be a consequence of membrane leakinessinduced by thionin treatment. In this respect, particularly striking wasthe parallelism found between 86Rb+ leakage and inhibition of proteinsynthesis by treatment with different genetic variants of thionins(alpha 1 purothionin, alpha 2 purothionin, beta purothionin from wheat;hordothionin from barley), as well as with the viscotoxins, which arehomologous polypeptides from the European mistletoe. Author.

Keyword(s): ANIMAL

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