Thevissen K, Ghazi A, De Samblanx G W, Brownlee C, Osborn R W, Broekaert W F
F. A. Janssens Laboratory of Genetics, Katholieke Universiteit Leuven, Willem de Croylaan 42, B-3001 Heverlee, Belgium.
J Biol Chem. 1996 Jun 21;271(25):15018-25. doi: 10.1074/jbc.271.25.15018.
Treatment of hyphae of Neurospora crassa with antifungal plant defensins, i.e. Rs-AFP2 and Dm-AMP1 isolated from radish and dahlia seed, respectively, induced a rapid K+ efflux, Ca2+ uptake, and alkalinization of the incubation medium. The Rs-AFP2-induced alkalinization of the incubation medium could be inhibited with G-protein inhibitors. alpha-Hordothionin, an antifungal thionin from barley seed, caused a sustained increased Ca2+ uptake at subinhibitory concentrations but only a transient increased uptake at inhibitory concentrations. alpha-Hordothionin also caused increased K+ efflux and alkalinization of the medium, but these fluxes occurred more rapidly compared to those caused by plant defensins. Furthermore, alpha-hordothionin caused permeabilization of fungal hyphae to the non-metabolite alpha-aminoisobutyric acid and, in addition, altered the electrical properties of artificial lipid bilayers, consistently leading to rupture of the lipid bilayers. The plant defensins did not form ion-permeable pores in artificial membranes and did not exhibit substantial hyphal membrane permeabilization activity. Our results are consistent with the notion that thionins inhibit fungal growth as a result of direct protein-membrane interactions, whereas plant defensins might act via a different, possibly receptor-mediated, mechanism.
用抗真菌植物防御素（即分别从萝卜和大丽花种子中分离出的Rs-AFP2和Dm-AMP1）处理粗糙脉孢菌的菌丝，会诱导快速的钾离子外流、钙离子内流以及培养基的碱化。Rs-AFP2诱导的培养基碱化可被G蛋白抑制剂抑制。α-大麦硫堇，一种来自大麦种子的抗真菌硫堇蛋白，在亚抑制浓度下会导致钙离子内流持续增加，但在抑制浓度下只会导致短暂的内流增加。α-大麦硫堇还会导致钾离子外流增加和培养基碱化，但与植物防御素引起的这些通量相比，这些通量出现得更快。此外，α-大麦硫堇会使真菌菌丝对非代谢物α-氨基异丁酸通透，并且还会改变人工脂质双层的电学性质，持续导致脂质双层破裂。植物防御素在人工膜中不会形成离子通透孔，也不表现出显著的菌丝膜通透活性。我们的结果与以下观点一致：硫堇蛋白通过直接的蛋白质-膜相互作用抑制真菌生长，而植物防御素可能通过不同的、可能是受体介导的机制起作用。
