Studies on Purothionin by Chemical Modifications1

Wada, Keishiro; Ozaki, Yasuhiko; Matsubara, Hiroshi; Yoshizumi, Hajime

doi:10.1093/oxfordjournals.jbchem.a133683

Cited by 46 publications

(39 citation statements)

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“…This was demonstrated by Wada et al (1982), who blocked all the amino groups of purothionin by acetyl or succinyl groups. This modification diminished the positive charges of the molecule and led to the loss of toxicity to mice or yeast.…”

Section: Electrostatic Interactions Are Essentialmentioning

confidence: 94%

Interaction of wheat α‐thionin with large unilamellar vesicles

Caaveiro

Molina

Rodrı́guez-Palenzuela

et al. 1998

Protein Science

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The interaction of the wheat antibacterial peptide a-thionin with large unilamellar vesicles has been investigated by means of fluorescence spectroscopy. Binding of the peptide to the vesicles is followed by the release of vesicle contents, vesicle aggregation, and lipid mixing. Vesicle fusion, i.e., mixing of the aqueous contents, was not observed. Peptide binding is governed by electrostatic interactions and shows no cooperativity. The amphipatic nature of wheat a-thionin seems to destabilize the membrane bilayer and trigger the aggregation of the vesicles and lipid mixing. The presence of distearoylphosphatidylethanolamine-poly(ethy1ene glycol 2000) (PEG-PE) within the membrane provides a steric barrier that inhibits vesicle aggregation and lipid mixing but does not prevent leakage. Vesicle leakage through discrete membrane channels is unlikely, because the release of encapsulated large fluorescent dextrans is very similar to that of 8-arninonaphthalene-l,3,6,trisulfonic acid (ANTS). A minimum number of 700 peptide molecules must bind to each vesicle to produce complete leakage, which suggests a mechanism in which the overall destabilization of the membrane is due to the formation of transient pores rather than discrete channels.

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Section: Electrostatic Interactions Are Essentialmentioning

confidence: 94%

Interaction of wheat α‐thionin with large unilamellar vesicles

Caaveiro

Molina

Rodrı́guez-Palenzuela

et al. 1998

Protein Science

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“…Iodination of ␤-Purothionin-2 mg of purified ␤-pth was iodinated using lactoperoxidase as per Wada et al (17). The extent of iodination of Tyr-13 was determined by MALDI-MS.…”

Section: Methodsmentioning

confidence: 99%

“…Divalent metal ions inhibit thionin toxicity (13,14), and 2-5 mM Ca 2ϩ is sufficient to completely protect cells, whereas calcium chelators increase the toxic effect of thionins (15). Iodination of tyrosine 13 of the Pyrularia pubera thionin, a residue found in all toxic thionins, leads to a loss of toxicity (16,17). This residue is absent only in the two nontoxic members of the thionin family the crambins (18).…”

mentioning

confidence: 99%

The Cytotoxic Plant Protein, β-Purothionin, Forms Ion Channels in Lipid Membranes

Hughes¹,

Dennis²,

Whitecross³

et al. 2000

Journal of Biological Chemistry

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Thionins are small cysteine-containing, amphipathic plant proteins found in seeds and vegetative tissues of a number of plant genera. Many of them have been shown to be toxic to microorganisms such as fungi, yeast, and bacteria and also to mammalian cells. It has been suggested that thionins are present in seeds to protect them, and the germinating seedling, from attack by phytopathogenic microorganisms, but the mechanism by which they kill cells remains unclear. Using electrophysiological measurements, we have shown that ␤-purothionin from wheat flour can form cation-selective ion channels in artificial lipid bilayer membranes and in the plasmalemma of rat hippocampal neurons. We suggest that the generalized toxicity of thionins is due to their ability to generate ion channels in cell membranes, resulting in the dissipation of ion concentration gradients essential for the maintenance of cellular homeostasis.

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“…The double helix folding, stabilized by the native-like Cys 6 -Cys 25 and Cys 10 -Cys 21 pairings, defines a characteristic amphipathic pattern and also contains residues shown to play a crucial role modulating thionin activity. Thus, iodination of Tyr 13 of PpTH leads to a loss of toxicity (43,44), suggesting that this residue is involved in the formation of transmembrane ion channels. Another sensitive position also present in our active, minimal versions of PpTH, is residue 32, the mutation of which (from Asp to Arg) significantly enhances activity against Gram-negative bacteria (17).…”

Section: Discussionmentioning

confidence: 99%

Structural Dissection of a Highly Knotted Peptide Reveals Minimal Motif with Antimicrobial Activity

Vila-Perelló

Sánchez‐Vallet²,

Garcı́a-Olmedo³

et al. 2005

Journal of Biological Chemistry

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The increasing occurrence of bacterial resistance to antibiotics is driving a renewed interest on antimicrobial peptides, in the hope that understanding the structural features responsible for their activity will provide leads into new anti-infective drug candidates. Most chemical studies in this field have focused on linear peptides of various eukaryotic origins, rather than on structures with complex folding patterns found also in nature. We have undertaken the structural dissection of a highly knotted, cysteine-rich plant thionin, with the aim of defining a minimal, synthetically accessible, structure that preserves the bioactive properties of the parent peptide. Using efficient strategies for directed disulfide bond formation, we have prepared a substantially simplified (45% size reduction) version with undiminished antimicrobial activity against a representative panel of pathogens. Analysis by circular dichroism shows that the downsized peptide preserves the central double ␣-helix of the parent form as an essential bioactive motif. Membrane permeability and surface plasmon resonance studies confirm that the mechanism of action remains unchanged.

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Studies on Purothionin by Chemical Modifications1

Cited by 46 publications

References 0 publications

Interaction of wheat α‐thionin with large unilamellar vesicles

Interaction of wheat α‐thionin with large unilamellar vesicles

The Cytotoxic Plant Protein, β-Purothionin, Forms Ion Channels in Lipid Membranes

Structural Dissection of a Highly Knotted Peptide Reveals Minimal Motif with Antimicrobial Activity

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