Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina, USA.
Department of Genetics, University of North Carolina, Chapel Hill, North Carolina, USA.
J Bacteriol. 2021 Jul 22;203(16):e0016521. doi: 10.1128/JB.00165-21.
The Yersinia pestis pH 6 antigen (PsaA) forms fimbria-like structures and is required for full virulence during bubonic plague. High temperature and low pH regulate PsaA production, and while recent work has uncovered the molecular aspects of temperature control, the mechanisms underlying this unusual regulation by pH are poorly understood. Using defined growth conditions, we recently showed that high levels of PsaE and PsaF (two regulatory proteins required for expression of ) are present at mildly acidic pH, but these levels are greatly reduced at neutral pH, resulting in low expression. In prior work, the use of translational reporters suggested that pH had no impact on translation of and , but rather affected protein stability of PsaE and/or PsaF. Here, we investigated the pH-dependent posttranslational mechanisms predicted to regulate PsaE and PsaF stability. Using antibodies that recognize the endogenous proteins, we showed that the amount of PsaE and PsaF is defined by a distinct pH threshold. Analysis of histidine residues in the periplasmic domain of PsaF suggested that it functions as a pH sensor and indicated that the presence of PsaF is important for PsaE stability. At neutral pH, when PsaF is absent, PsaE appears to be targeted for proteolytic degradation by regulated intramembrane proteolysis. Together, our work shows that Y. pestis utilizes PsaF as a pH sensor to control expression by enhancing the stability of PsaE, an essential regulatory protein. Yersinia pestis is a bacterial pathogen that causes bubonic plague in humans. As Y. pestis cycles between fleas and mammals, it senses the environment within each host to appropriately control gene expression. PsaA is a protein that forms fimbria-like structures and is required for virulence. High temperature and low pH together stimulate transcription by increasing the levels of two essential integral membrane regulators, PsaE and PsaF. Histidine residues in the PsaF periplasmic domain enable it to function as a pH sensor. In the absence of PsaF, PsaE (a DNA-binding protein) appears to be targeted for proteolytic degradation, thus preventing expression of . This work offers insight into the mechanisms that bacteria use to sense pH and control virulence gene expression.
鼠疫耶尔森氏菌 pH6 抗原（PsaA）形成菌毛样结构，在腺鼠疫中是完全毒力所必需的。高温和低 pH 值调节 PsaA 的产生，虽然最近的工作揭示了温度控制的分子方面，但 pH 值调节的机制还知之甚少。使用明确的生长条件，我们最近表明，在轻度酸性 pH 值下存在高水平的 PsaE 和 PsaF（表达所必需的两种调节蛋白），但在中性 pH 值下这些水平大大降低，导致低水平的表达。在之前的工作中，翻译报告基因的使用表明 pH 值对翻译没有影响，而是影响 PsaE 和/或 PsaF 的蛋白质稳定性。在这里，我们研究了预测调节 PsaE 和 PsaF 稳定性的 pH 依赖性翻译后机制。使用识别内源性蛋白的抗体，我们表明 PsaE 和 PsaF 的量由一个独特的 pH 值阈值定义。对 PsaF 周质域中组氨酸残基的分析表明，它作为 pH 值传感器发挥作用，并表明 PsaF 的存在对于 PsaE 的稳定性很重要。在中性 pH 值时，当 PsaF 不存在时，PsaE 似乎被靶向通过调节性内膜蛋白水解进行降解。总之，我们的工作表明，鼠疫耶尔森氏菌利用 PsaF 作为 pH 值传感器通过增强关键调节蛋白 PsaE 的稳定性来控制表达。鼠疫耶尔森氏菌是一种细菌病原体，可引起人类腺鼠疫。当鼠疫耶尔森氏菌在跳蚤和哺乳动物之间循环时，它会感知每个宿主内的环境，以适当控制基因表达。PsaA 是一种形成菌毛样结构的蛋白质，是毒力所必需的。高温和低 pH 值共同通过增加两种必需的整合膜调节剂 PsaE 和 PsaF 的水平来刺激转录。PsaF 周质域中的组氨酸残基使其能够作为 pH 值传感器发挥作用。在没有 PsaF 的情况下，PsaE（一种 DNA 结合蛋白）似乎被靶向进行蛋白水解降解，从而阻止的表达。这项工作深入了解了细菌用来感知 pH 值和控制毒力基因表达的机制。
