Puroindolines form ion channels in biological membranes.
Wheat seeds contain different lipid binding proteins that are low molecular mass, basic and cystine-rich proteins. Among them, the recently characterized puroindolines have been shown to inhibit the growth of fungi in vitro and to enhance the fungal resistance of plants. Experimental data, using lipid vesicles, suggest that this antimicrobial activity is related to interactions with cellular membranes, but the underlying mechanisms are still unknown. This paper shows that extracellular application of puroindolines on voltage-clamped Xenopus laevis oocytes induced membrane permeabilization. Electrophysiological experiments, on oocytes and artificial planar lipid bilayers, suggest the formation, modulated by voltage, of cation channels with the following selectivity: Cs(+) > K(+) > Na(+) > Li(+) > choline = TEA. Furthermore, this channel activity was prevented by addition of Ca(2+) ions in the medium. Puroindolines were also able to decrease the long-term oocyte viability in a voltage-dependent manner. Taken together, these results indicate that channel formation is one of the mechanisms by which puroindolines exert their antimicrobial activity. Modulation of channel formation by voltage, Ca(2+), and lipids could introduce some selectivity in the action of puroindolines on natural membranes.
Charnet
Pierre
P
Centre de Recherche de Biochimie Moléculaire, CNRS UPR 1086, UFR 24, 1919, 34293 Montpellier, France. charnet@crbm.cnrs-mop.fr
Molle
Gérard
G
Marion
Didier
D
Rousset
Matthieu
M
Lullien-Pellerin
Valérie
V
D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004553:Electric Conductivity; D015640:Ion Channel Gating / Q000187:drug effects; D007473:Ion Channels / Q000737:chemistry* / Q000502:physiology*; D008051:Lipid Bilayers / Q000737:chemistry; D008564:Membrane Potentials; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D010940:Plant Proteins / Q000737:chemistry* / Q000494:pharmacology*; D012639:Seeds / Q000737:chemistry; D014908:Triticum / Q000737:chemistry; D014982:Xenopus laevis
D007473:Ion Channels; D008051:Lipid Bilayers; D010940:Plant Proteins; C082942:puroindoline protein, Triticum aestivum