Department of Molecular Biology, Cell Biology and Biochemistry, Laboratories of Molecular Medicine Brown University, Providence, Rhode Island, USA.
Protein Sci. 2021 Apr;30(4):899-907. doi: 10.1002/pro.4047. Epub 2021 Mar 1.
In the model organism Escherichia coli and related species, the general stress response relies on tight regulation of the intracellular levels of the promoter specificity subunit RpoS. RpoS turnover is exclusively dependent on RssB, a two-domain response regulator that functions as an adaptor that delivers RpoS to ClpXP for proteolysis. Here, we report crystal structures of the receiver domain of RssB both in its unphosphorylated form and bound to the phosphomimic BeF . Surprisingly, we find only modest differences between these two structures, suggesting that truncating RssB may partially activate the receiver domain to a "meta-active" state. Our structural and sequence analysis points to RssB proteins not conforming to either the Y-T coupling scheme for signaling seen in prototypical response regulators, such as CheY, or to the signaling model of the less understood FATGUY proteins.
在模式生物大肠杆菌和相关物种中，一般应激反应依赖于严格调节启动子特异性亚基 RpoS 的细胞内水平。RpoS 的周转完全依赖于 RssB，这是一种具有两个结构域的响应调节蛋白，作为一种衔接蛋白，将 RpoS 递送给 ClpXP 进行蛋白水解。在这里，我们报告了 RssB 的受体结构域的晶体结构，分别处于非磷酸化形式和与磷酸模拟物 BeF 结合的形式。令人惊讶的是，我们发现这两种结构之间只有微小的差异，这表明截短 RssB 可能会将受体结构域部分激活到“元活性”状态。我们的结构和序列分析表明，RssB 蛋白不符合典型的响应调节剂（如 CheY）中看到的 Y-T 偶联信号方案，也不符合不太了解的 FATGUY 蛋白的信号模型。
