As the universal methyl donor for methylation reactions, S-adenosylmethionine (AdoMet) plays an indispensable role in most cellular metabolic processes. AdoMet is synthesized by AdoMet synthetase. We identified the only one AdoMet synthetase (PoSasA) in filamentous fungus Penicillium oxalicum. PoSasA was widely distributed in mycelium at different growth stages. The absence of PoSasA was lethal for P. oxalicum. The misregulation of the PoSasA encoding gene affected the synthesis of extracellular cellulolytic enzymes. The expression levels of cellobiohydrolase encoding gene cbh1/cel7A, β-1-4 endoglucanase eg1/cel7B, and xylanase encoding gene xyn10A were remarkably downregulated as a result of decreased PosasA gene expression. The production of extracellular cellulases and hemicellulases was also reduced. By contrast, the overexpression of PosasA improved the production of extracellular cellulases and hemicellulases. A total of 133 putative interacting proteins with PoSasA were identified using tandem affinity purification and mass spectrometry. The results of functional enrichment on these proteins showed that they were mainly related to ATP binding, magnesium ion binding, and ATP synthetase activity. Several methyltransferases were also observed among these proteins. These results were consistent with the intrinsic feature of AdoMet synthetase. This work reveals the indispensable role of PoSasA in various biological processes.

中文翻译：

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草酸青霉 S-腺苷甲硫氨酸合成酶对真菌细胞的活力和编码纤维素分解酶的基因的表达至关重要

作为甲基化反应的通用甲基供体，S-腺苷甲硫氨酸（AdoMet）在大多数细胞代谢过程中起着不可或缺的作用。AdoMet 由 AdoMet 合成酶合成。我们在丝状真菌草酸青霉中鉴定了唯一一种 AdoMet 合成酶 (PoSasA)。PoSasA广泛分布于不同生长阶段的菌丝体中。PoSasA 的缺失对草酸假单胞菌是致命的。PoSasA 编码基因的错误调节影响了细胞外纤维素分解酶的合成。由于 PosasA 基因表达降低，纤维二糖水解酶编码基因 cbh1/cel7A、β-1-4 内切葡聚糖酶 eg1/cel7B 和木聚糖酶编码基因 xyn10A 的表达水平显着下调。细胞外纤维素酶和半纤维素酶的产生也减少了。相比之下，PosasA 的过表达提高了细胞外纤维素酶和半纤维素酶的产生。使用串联亲和纯化和质谱法鉴定了总共 133 种推定的与 PoSasA 相互作用的蛋白质。对这些蛋白质的功能富集结果表明，它们主要与ATP结合、镁离子结合和ATP合成酶活性有关。在这些蛋白质中也观察到了几种甲基转移酶。这些结果与 AdoMet 合成酶的内在特征一致。这项工作揭示了 PoSasA 在各种生物过程中不可或缺的作用。对这些蛋白质的功能富集结果表明，它们主要与ATP结合、镁离子结合和ATP合成酶活性有关。在这些蛋白质中也观察到了几种甲基转移酶。这些结果与 AdoMet 合成酶的内在特征一致。这项工作揭示了 PoSasA 在各种生物过程中不可或缺的作用。对这些蛋白质的功能富集结果表明，它们主要与ATP结合、镁离子结合和ATP合成酶活性有关。在这些蛋白质中也观察到了几种甲基转移酶。这些结果与 AdoMet 合成酶的内在特征一致。这项工作揭示了 PoSasA 在各种生物过程中不可或缺的作用。