Biology subjects

Brugger, C.

Publications and source records attributed to Brugger, C..

3 recordsLinked to original sources

bioRxiv2023

IraM Remodels the RssB Segmented Helical Linker to Stabilize σs against Degradation by ClpXP

Upon Mg2+ starvation, a condition often associated with virulence, enterobacteria inhibit the ClpXP-dependent proteolysis of the master transcriptional regulator, {sigma}s, via IraM, a poorly understood anti-adaptor that prevents RssB-dependent loading of {sigma}s onto ClpXP. This inhibition results in {sigma}s accumulation, and expression of stress resistance genes. Here we report on the structural analysis of RssB bound to IraM, which reveals that IraM induces two folding transitions within RssB, which are amplified via a segmental helical linker. This work highlights the remarkable structural plasticity of RssB and reveals how a stress-specific RssB antagonist modulates a core stress response pathway that could be leveraged to control biofilm formation, virulence, and the development of antibiotic resistance.

biophysics↗

bioRxiv2022

Structure of Phosphorylated-like ClpXP Adaptor RssB Reveals an Interface Switch for Activation

SUMMARYIn {gamma}-proteobacteria such as Escherichia coli, the general stress response is mediated by {sigma}s, the stationary phase dissociable promoter specificity subunit of RNA polymerase. {sigma}s is degraded by ClpXP during active growth in a process dependent on the RssB adaptor, which acts catalytically and is thought to be stimulated by phosphorylation of a conserved aspartate in its N-terminal receiver domain. Here we present the crystal structure of full-length RssB bound to a beryllofluoride phosphomimic. Compared to the inhibited IraD anti-adaptor-bound RssB structure, our study reveals movements and coil-to-helix transitions in the C-terminal region of the RssB receiver domain and in the inter-domain segmented helical linker, accompanied by packing of the C-terminal effector domain onto the 4-{beta}5-5 (4-5-5) "signaling" face of the RssB receiver domain. This face is often the locus of protein-protein interactions in unphosphorylated receiver domains, but its masking is unusual in their phosphorylated forms. Our structure emphasizes the remarkable plasticity that underpins regulatory strategies within the large family of response regulators.

biophysics↗

bioRxiv2021

Phospho-dependent Signaling during the General Stress Response by the Atypical Response Regulator and ClpXP Adaptor RssB

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 BeF3-. 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.

biophysics↗