Bacterial spores can remain dormant for decades yet rapidly germinate and resume growth in response to nutrients. GerA family receptors that sense and respond to these signals have recently been shown to oligomerize into nutrient-gated ion channels. Ion release initiates exit from dormancy. Here, we report that a distinct ion channel, composed of SpoVAF (5AF) and its newly discovered partner protein, YqhR (FigP), amplifies the response. At high germinant concentrations, 5AF/FigP accelerate germination; at low concentrations, this complex becomes critical for exit from dormancy. 5AF is homologous to the channel-forming subunit of GerA family receptors and is predicted to oligomerize around a central pore. 5AF mutations predicted to widen the channel cause constitutive germination during spore formation and membrane depolarization in vegetative cells. Narrow-channel mutants are impaired in germination. A screen for suppressors of a constitutively germinating 5AF mutant identified FigP as an essential cofactor of 5AF activity. We demonstrate that 5AF and FigP interact and colocalize with GerA family receptors in spores. Finally, we show that 5AF/FigP accelerate germination in B. subtilis spores that have nutrient receptors from another species. Our data support a model in which nutrient-triggered ion release by GerA family receptors activates 5AF/FigP ion release, amplifying the response to germinant signals.

中文翻译：

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SpoVAF 和 FigP 组装成寡聚离子通道，增强孢子萌发

细菌孢子可以休眠数十年，但会根据营养物质迅速发芽并恢复生长。最近表明，感知和响应这些信号的 GerA 家族受体寡聚化成营养门控离子通道。离子释放启动退出休眠状态。在这里，我们报告了由 SpoVAF (5AF) 及其新发现的伙伴蛋白 YqhR (FigP) 组成的独特离子通道放大了反应。在高发芽浓度下，5AF/FigP 可加速发芽；在低浓度下，该复合物对于退出休眠至关重要。5AF 与 GerA 家族受体的通道形成亚基同源，预计会在中心孔周围寡聚化。5AF突变预计会拓宽通道，导致营养细胞孢子形成和膜去极化期间的组成型萌发。窄通道突变体的萌发受到损害。对组成型萌发 5AF 突变体的抑制子的筛选确定 FigP 是 5AF 活性的重要辅助因子。我们证明 5AF 和 FigP 与孢子中的 GerA 家族受体相互作用并共定位。最后，我们发现 5AF/FigP 可以加速具有其他物种营养受体的枯草芽孢杆菌孢子的萌发。我们的数据支持一个模型，其中 GerA 家族受体营养触发的离子释放激活 5AF/FigP 离子释放，放大对萌芽信号的反应。