Streptococcus anginosus is frequently detected in patients with infective endocarditis, abscesses or oral cancer. Although S. anginosus is considered the causative pathogen of these diseases, the pathogenic mechanisms of the bacterium have remained unclear. Previously, we suggested that an extracellular antigen from S. anginosus (SAA) serves as a pathogenic factor by inducing nitric oxide production in murine macrophages. In the present study, we identified SAA using LC–MS/MS and assessed the biological activities of His-tagged recombinant SAA in murine macrophages. SAA was identified as a tyrosine tRNA synthetase (SaTyrRS) that was isolated from the extracellular fraction of S. anginosus but not from other oral streptococci. In addition, inducible nitric oxide synthase and TNF-α mRNA expression was induced in recombinant SaTyrRS-stimulated murine macrophages. However, their mRNA expression was not induced in macrophages stimulated with truncated or heat-inactivated recombinant SaTyrRS, and the activation motif was identified as Arg²⁶⁴–Thr²⁷⁰. Consequently, these results indicated that SaTyrRS could be a novel and specific immunomodulatory protein in S. anginosus.

中文翻译：

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酪氨酸 tRNA 合成酶作为心绞痛链球菌中一种新型细胞外免疫调节蛋白。

链球菌心绞痛经常在感染性心内膜炎、脓肿或口腔癌患者中检测到。尽管心绞痛链球菌被认为是这些疾病的病原体，但该细菌的致病机制仍不清楚。以前，我们建议来自心绞痛链球菌(SAA)的细胞外抗原通过诱导小鼠巨噬细胞产生一氧化氮作为致病因子。在本研究中，我们使用 LC-MS/MS 鉴定了 SAA，并评估了带有 His 标签的重组 SAA 在鼠巨噬细胞中的生物活性。SAA被鉴定为酪氨酸-tRNA合成酶（SaTyrRS），这是从胞外部分分离S.咽峡炎但不是来自其他口腔链球菌。此外，在重组 SaTyrRS 刺激的小鼠巨噬细胞中诱导诱导型一氧化氮合酶和 TNF-α mRNA 表达。然而，在用截短的或热灭活的重组 SaTyrRS 刺激的巨噬细胞中，它们的 mRNA 表达没有被诱导，激活基序被鉴定为 Arg ²⁶⁴ –Thr ²⁷⁰。因此，这些结果表明 SaTyrRS 可能是S. anginosus 中一种新型的特异性免疫调节蛋白。