Starvation of Bacillus subtilis initiates endosporulation involving formation of mother cell (MC) and forespore (FS) compartments. During engulfment, the MC membrane migrates around the FS and protein channels connect the two compartments. The channels are necessary for postengulfment FS gene expression, which relieves inhibition of SpoIVFB, an intramembrane protease that cleaves Pro‐σ^K, releasing σ^K into the MC. SpoIVFB has an ATP‐binding domain exposed to the MC cytoplasm, but the role of ATP in regulating Pro‐σ^K cleavage has been unclear, as has the impact of the channels on MC and FS ATP levels. Using luciferase produced separately in each compartment to measure relative ATP concentrations during sporulation, we found that the MC ATP concentration rises about twofold coincident with increasing cleavage of Pro‐σ^K, and the FS ATP concentration does not decline. Mutants lacking a channel protein or defective in channel protein turnover exhibited modest and varied effects on ATP levels, which suggested that low ATP concentration does not explain the lack of postengulfment FS gene expression in channel mutants. Furthermore, a rise in the MC ATP level was not necessary for Pro‐σ^K cleavage by SpoIVFB, based on analysis of mutants that bypass the need for relief of SpoIVFB inhibition.

中文翻译：

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通道在枯草芽孢杆菌孢子形成过程中适度影响隔室特异性 ATP 水平，并且母细胞 ATP 水平的升高对于 Pro-σK 裂解不是必需的。

枯草芽孢杆菌的饥饿启动内孢子形成，涉及母细胞 (MC) 和前孢子 (FS) 隔室的形成。在吞没过程中，MC 膜在 FS 周围迁移，蛋白质通道连接两个隔室。这些通道是吞噬后 FS 基因表达所必需的，这会减轻 SpoIVFB 的抑制，SpoIVFB 是一种膜内蛋白酶，可裂解 Pro-σ ^K，将σ ^K释放到 MC 中。SpoIVFB 具有暴露于 MC 细胞质的 ATP 结合域，但 ATP 在调节 Pro-σ ^{K 中的作用}裂解尚不清楚，通道对 MC 和 FS ATP 水平的影响也不清楚。使用在每个隔室中单独产生的荧光素酶来测量孢子形成过程中的相对 ATP 浓度，我们发现 MC ATP 浓度随着 Pro-σ ^K裂解的增加而增加约两倍，而 FS ATP 浓度没有下降。缺乏通道蛋白或通道蛋白周转缺陷的突变体对 ATP 水平表现出适度和不同的影响，这表明低 ATP 浓度不能解释通道突变体中缺乏吞噬后 FS 基因表达。此外，基于对绕过缓解 SpoIVFB 抑制需要的突变体的分析，MC ATP 水平的升高对于SpoIVFB 的Pro-σ ^K裂解不是必需的。