Cysteine oxidations play important regulatory roles during animal virus infections. Despite the importance of redox modifications during plant infections, no plant virus protein has yet been shown to be regulated by cysteine oxidation. The potexvirus pepino mosaic virus (PepMV) is pandemic in tomato crops. Previously we modeled the structure of the PepMV particle and coat protein (CP) by cryo-electron microscopy and identified critical residues of the CP RNA-binding pocket that interact with the viral RNA during particle formation and viral cell-to-cell movement. The PepMV CP has a single cysteine residue (Cys127) central to its RNA binding pocket, which is highly conserved. Here we show that the Cys127Ser replacement diminishes PepMV fitness, and that PepMV CPWT is oxidized in vivo while CPC127S is not. We also show that Cys127 gets spontaneously glutathionylated in vitro, and that S-glutathionylation blocks in vitro the formation of virion-like particles (VLPs). VLPs longer than 200 nm could be formed after in planta CPC127S overexpression, while very short and dispersed VLPs were observed after CPWT overexpression. Our results strongly suggest that the CP redox status regulates CP functions via cysteine oxidation.

中文翻译：

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凤梨花叶病毒外壳蛋白氧化还原状态的调节作用。

半胱氨酸氧化在动物病毒感染过程中发挥重要的调节作用。尽管氧化还原修饰在植物感染过程中很重要，但尚未显示植物病毒蛋白受到半胱氨酸氧化的调节。马铃薯花叶病毒 (PepMV) 在番茄作物中流行。此前，我们通过冷冻电子显微镜对 PepMV 颗粒和外壳蛋白 (CP) 的结构进行了建模，并鉴定了 CP RNA 结合口袋的关键残基，这些残基在颗粒形成和病毒细胞间运动过程中与病毒 RNA 相互作用。PepMV CP 在其 RNA 结合袋中央有一个高度保守的半胱氨酸残基 (Cys127)。在这里，我们表明 Cys127Ser 替代会降低 PepMV 的适应性，并且 PepMV CPWT 在体内被氧化，而 CPC127S 则不会。我们还表明，Cys127 在体外自发谷胱甘肽化，并且 S-谷胱甘肽化在体外阻断病毒颗粒样颗粒 (VLP) 的形成。植物体内CPC127S过表达后可形成长度超过200 nm的VLP，而CPWT过表达后观察到非常短且分散的VLP。我们的结果强烈表明 CP 氧化还原状态通过半胱氨酸氧化调节 CP 功能。