The cytotoxic plant protein, beta-purothionin, forms ion channels in lipid membranes.
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 beta-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.
Hughes
P
P
CSIRO Plant Industry, Clunies Ross St., Canberra, Australian Capital Territory 2601, Australia.
Dennis
E
E
Whitecross
M
M
Llewellyn
D
D
Gage
P
P
D000818:Animals; D023181:Antimicrobial Cationic Peptides; D002462:Cell Membrane / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects; D004594:Electrophysiology; D005433:Flour; D006624:Hippocampus / Q000502:physiology; D007473:Ion Channels / Q000737:chemistry*; D007941:Leukemia P388; D008051:Lipid Bilayers; D051379:Mice; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000187:drug effects; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity; D011487:Protein Conformation; D051381:Rats; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014118:Toxins, Biological / Q000737:chemistry; D014908:Triticum; D014407:Tumor Cells, Cultured
D023181:Antimicrobial Cationic Peptides; D007473:Ion Channels; D008051:Lipid Bilayers; D010940:Plant Proteins; D014118:Toxins, Biological; C016085:purothionin