Jeenkeawpieam Juthatip, Yodkeeree Supachai, Andrianopoulos Alex, Roytrakul Sittiruk, Pongpom Monsicha
Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
Department of Biochemistry, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
J Fungi (Basel). 2020 Dec 3;6(4):333. doi: 10.3390/jof6040333.
Antifungal proteins (AFPs) are able to inhibit a wide spectrum of fungi without significant toxicity to the hosts. This study examined the antifungal activity of AFPs isolated from a Thai medicinal plant, against the human pathogenic fungus . This dimorphic fungus causes systemic infections in immunocompromised individuals and is endemic in Southeast Asian countries. The crude protein extract inhibited the growth of . The anti- activity was completely lost when treated with proteinase K and pepsin, indicating that the antifungal activity was dependent on a protein component. The total protein extract from was partially purified by size fractionation to ≤10, 10-30, and ≥30 kDa fractions and tested for the minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC). All fractions showed anti- activity with the MIC and MFC values of 32 to 128 μg/mL and >128 μg/mL, respectively. In order to determine the mechanism of inhibition, all fractions were tested with mutant strains affected in G-protein signaling and cell wall integrity pathways. The anti- activity of the 10-30 kDa fraction was abrogated by deletion of and , the genes encoding alpha subunits of heterotrimeric G-proteins, indicating that the inhibitory effect is related to intracellular signaling through G-proteins. The work demonstrates that antifungal proteins isolated from represent sources for novel drug development.
抗真菌蛋白（AFPs）能够抑制多种真菌，且对宿主无明显毒性。本研究检测了从一种泰国药用植物中分离出的AFPs对人类致病真菌的抗真菌活性。这种双态真菌在免疫功能低下的个体中引起全身感染，在东南亚国家呈地方性流行。该粗蛋白提取物抑制了该真菌的生长。当用蛋白酶K和胃蛋白酶处理时，抗真菌活性完全丧失，这表明抗真菌活性依赖于一种蛋白质成分。从该植物中提取的总蛋白提取物通过尺寸分级法进行部分纯化，得到分子量≤10 kDa、10 - 30 kDa和≥30 kDa的级分，并检测其最小抑菌浓度（MIC）和最小杀菌浓度（MFC）。所有级分均显示出抗真菌活性，MIC和MFC值分别为32至128 μg/mL和>128 μg/mL。为了确定抑制机制，所有级分都用在G蛋白信号传导和细胞壁完整性途径中受影响的突变菌株进行了测试。10 - 30 kDa级分的抗真菌活性因编码异源三聚体G蛋白α亚基的基因Gα和Gβ的缺失而被消除，这表明抑制作用与通过G蛋白的细胞内信号传导有关。这项工作表明，从该植物中分离出的抗真菌蛋白是新型药物开发的来源。
