title: The antifungal plant defensin AtPDF2.3 from Arabidopsis thaliana blocks potassium channels.
abstract: Scorpion toxins that block potassium channels and antimicrobial plant defensins share a common structural CSαβ-motif. These toxins contain a toxin signature (K-C4-X-N) in their amino acid sequence, and based on in silico analysis of 18 plant defensin sequences, we noted the presence of a toxin signature (K-C5-R-G) in the amino acid sequence of the Arabidopsis thaliana defensin AtPDF2.3. We found that recombinant (r)AtPDF2.3 blocks Kv1.2 and Kv1.6 potassium channels, akin to the interaction between scorpion toxins and potassium channels. Moreover, rAtPDF2.3[G36N], a variant with a KCXN toxin signature (K-C5-R-N), is more potent in blocking Kv1.2 and Kv1.6 channels than rAtPDF2.3, whereas rAtPDF2.3[K33A], devoid of the toxin signature, is characterized by reduced Kv channel blocking activity. These findings highlight the importance of the KCXN scorpion toxin signature in the plant defensin sequence for blocking potassium channels. In addition, we found that rAtPDF2.3 inhibits the growth of Saccharomyces cerevisiae and that pathways regulating potassium transport and/or homeostasis confer tolerance of this yeast to rAtPDF2.3, indicating a role for potassium homeostasis in the fungal defence response towards rAtPDF2.3. Nevertheless, no differences in antifungal potency were observed between the rAtPDF2.3 variants, suggesting that antifungal activity and Kv channel inhibitory function are not linked.
authors: Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium.
authors: Kim
authors: K
authors: Vriens
authors: Toxicology and Pharmacology, University of Leuven, O&N 2, Herestraat 49, P.O. Box 922, 3000, Leuven, Belgium.
authors: Steve
authors: S
authors: Peigneur
authors: Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium.|VIB Department of Plant Systems Biology, Technologiepark 927, 9052 Ghent, Belgium.
authors: Barbara
authors: B
authors: De Coninck
authors: Toxicology and Pharmacology, University of Leuven, O&N 2, Herestraat 49, P.O. Box 922, 3000, Leuven, Belgium.
authors: Jan
authors: J
authors: Tytgat
authors: Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium.|VIB Department of Plant Systems Biology, Technologiepark 927, 9052 Ghent, Belgium.
authors: Bruno P A
authors: BP
authors: Cammue
authors: Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium.
authors: Karin
authors: K
authors: Thevissen
mesh_terms: D000935:Antifungal Agents / Q000737:chemistry / Q000494:pharmacology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D006801:Humans; D051663:Kv1.2 Potassium Channel / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D051667:Kv1.6 Potassium Channel; D026902:Potassium Channel Blockers / Q000737:chemistry / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D051637:Shaker Superfamily of Potassium Channels / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: D000935:Antifungal Agents; D029681:Arabidopsis Proteins; D018398:Homeodomain Proteins; C064389:KCNA6 protein, human; D051663:Kv1.2 Potassium Channel; D051667:Kv1.6 Potassium Channel; C472305:PDF2 protein, Arabidopsis; D026902:Potassium Channel Blockers; D011994:Recombinant Proteins; D051637:Shaker Superfamily of Potassium Channels