The stationary phase promoter specificity subunit σS (RpoS) is delivered to the ClpXP machinery for degradation dependent on the adaptor RssB. This adaptor-specific degradation of σS provides a major point for regulation and transcriptional reprogramming during the general stress response. RssB is an atypical response regulator and the only known ClpXP adaptor that is inhibited by multiple but dissimilar antiadaptors (IraD, IraP, and IraM). These are induced by distinct stress signals and bind to RssB in poorly understood manners to achieve stress-specific inhibition of σS turnover. Here we present the first crystal structure of RssB bound to an antiadaptor, the DNA damage-inducible IraD. The structure reveals that RssB adopts a compact closed architecture with extensive interactions between its N-terminal and C-terminal domains. The structural data, together with mechanistic studies, suggest that RssB plasticity, conferred by an interdomain glutamate-rich flexible linker, is critical for regulation of σS degradation. Structural modulation of interdomain linkers may thus constitute a general strategy for tuning response regulators.

中文翻译：

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ClpXP抗调节剂抑制σS稳定性响应调节剂的结构基础。

固定相启动子特异性亚基σS（RpoS）被传递到ClpXP机械中，取决于接头RssB的降解。σS的这种衔接子特异性降解为一般应激反应期间的调控和转录重编程提供了主要依据。RssB是一个非典型反应调节剂，并且是唯一已知的ClpXP衔接子，它被多种但不相似的抗适配器（IraD，IraP和IraM）抑制。这些是由不同的应力信号诱导的，并以鲜为人知的方式与RssB结合，以实现σS转换的应力特异性抑制。在这里，我们介绍结合抗适配器，DNA损伤诱导的IraD的RssB的第一个晶体结构。该结构表明，RssB采用紧凑的封闭结构，在其N端和C端结构域之间具有广泛的相互作用。结构数据以及机理研究表明，域间富含谷氨酸的柔性接头赋予RssB可塑性，对于调节σS降解至关重要。域间连接子的结构调制因此可以构成用于调节响应调节器的一般策略。