Crystal structure of rice defensin OsAFP1 and molecular insight into lipid-binding
Crystal structure of rice defensin OsAFP1 and molecular insight into lipid-binding
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DOI：
10.1016/j.jbiosc.2020.02.011
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发表时间：
2020-07-01
影响因子：
2.8
通讯作者：
Taniguchi, Masayuki
中科院分区：
文献类型：
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作者：
Ochiai, Akihito;Ogawa, Kodai;Taniguchi, Masayuki
防御素是在先天免疫系统中发挥作用的抗菌肽。 OsAFP1 是从 Oryza sativa（水稻）中鉴定出的一种防御素，对水稻病原体具有抗菌活性。有趣的是，OsAFP1 还被证明通过诱导靶细胞凋亡，对人类致病真菌白色念珠菌具有有效的抗真菌活性，这表明 OsAFP1 代表了一种潜在的新抗生素候选者。然而，需要进一步的分析，特别是在结构水平上，以阐明 OsAFP1 抗真菌活性的机制基础。在这里，我们使用 X 射线晶体学确定了 OsAFP1 的三维结构。 OsAFP1 具有在植物防御素中高度保守的半胱氨酸稳定的 ab 结构，并呈现出抗真菌活性所必需的二聚体结构。 OsAFP1 结构与与磷脂酸复合的烟草 NaD1 结构的叠加表明，目标分子可能被捕获在每个 OsAFP1 二聚体的 S2-S3 环之间。在使用固定有各种膜脂质成分的硝化纤维素膜进行的脂质结合分析中，发现 OsAFP1 与含有磷酸基团的磷脂酰肌醇 (PIP) 结合，特别是 PI(3)P。这些结果表明OsAFP1通过与白色念珠菌细胞膜中含有的PI(3)P结合而发挥抗真菌活性，从而施加细胞应激并诱导细胞凋亡。此外，OsAFP1 结构和位点特异性突变分析表明，Arg1、His2、Leu4、Arg9 和 Phe10 在 OsAFP1 二聚体形成中发挥关键作用。因此，我们的研究为 OsAFP1 的抗真菌机制提供了新的见解。 (C) 2020，日本生物技术协会。版权所有。
Defensins are antibacterial peptides that function in the innate immune system. OsAFP1, a defensin identified from Oryza sativa (rice), exhibits antimicrobial activity against rice pathogens. Intriguingly, OsAFP1 was also shown to demonstrate potent antifungal activity against the human pathogenic fungus Candida albicans by inducing apoptosis in target cells, suggesting that OsAFP1 represents a potential new antibiotic candidate; however, further analyses, particularly at the structural level, are required to elucidate the mechanistic underpinnings of OsAFP1 antifungal activity. Here, we determined the three-dimensional structure of OsAFP1 using X-ray crystallography. OsAFP1 features the cysteine-stabilized ab structure highly conserved in plant defensins and presents a dimeric structure that appears necessary for antifungal activity. Superimposition of the OsAFP1 structure with that of Nicotiana alata NaD1 complexed with phosphatidic acid indicated that the target molecule is likely trapped between the S2-S3 loops of each OsAFP1 dimer. In lipid-binding analyses performed using nitrocellulose membranes immobilized with various membrane lipid components, OsAFP1 was found to bind to phosphatidylinositols (PIPs) harboring phosphate groups, particularly PI(3)P. These results indicate that OsAFP1 exerts antifungal activity by binding to PI(3)P contained in the C. albicans cell membrane, thereby applying cellular stress and inducing apoptosis. Furthermore, the OsAFP1 structure and site-specific-mutation analyses revealed that Arg1, His2, Leu4, Arg9, and Phe10 play critical roles in OsAFP1 dimer formation. Thus, our study provides novel insights into the antifungal mechanism of OsAFP1. (C) 2020, The Society for Biotechnology, Japan. All rights reserved.