A Novel Redox-Sensing Histidine Kinase That Controls Carbon Catabolite Repression in Azoarcus sp. CIB

Abstract

We have identified and characterized the AccS multidomain sensor kinase that mediates the activation of the AccR master regulator involved in carbon catabolite repression (CCR) of the anaerobic catabolism of aromatic compounds inAzoarcussp. CIB. A truncated AccS protein that contains only the soluble C-terminal autokinase module (AccS′) accounts for the succinate-dependent CCR control. In vitroassays with purified AccS′ revealed its autophosphorylation, phosphotransfer from AccS′∼P to the Asp60 residue of AccR, and the phosphatase activity toward its phosphorylated response regulator, indicating that the equilibrium between the kinase and phosphatase activities of AccS′ may control the phosphorylation state of the AccR transcriptional regulator. Oxidized quinones, e.g., ubiquinone 0 and menadione, switched the AccS′ autokinase activity off, and three conserved Cys residues, which are not essential for catalysis, are involved in such inhibition. Thiol oxidation by quinones caused a change in the oligomeric state of the AccS′ dimer resulting in the formation of an inactive monomer. This thiol-based redox switch is tuned by the cellular energy state, which can change depending on the carbon source that the cells are using. This work expands the functional diversity of redox-sensitive sensor kinases, showing that they can control new bacterial processes such as CCR of the anaerobic catabolism of aromatic compounds. The AccSR two-component system is conserved in the genomes of some betaproteobacteria, where it might play a more general role in controlling the global metabolic state according to carbon availability.IMPORTANCETwo-component signal transduction systems comprise a sensor histidine kinase and its cognate response regulator, and some have evolved to sense and convert redox signals into regulatory outputs that allow bacteria to adapt to the altered redox environment. The work presented here expands knowledge of the functional diversity of redox-sensing kinases to control carbon catabolite repression (CCR), a phenomenon that allows the selective assimilation of a preferred compound among a mixture of several carbon sources. The newly characterized AccS sensor kinase is responsible for the phosphorylation and activation of the AccR master regulator involved in CCR of the anaerobic degradation of aromatic compounds in the betaproteobacteriumAzoarcussp. CIB. AccS seems to have a thiol-based redox switch that is modulated by the redox state of the quinone pool. The AccSR system is conserved in several betaproteobacteria, where it might play a more general role controlling their global metabolic state.

Advances in the identification of signals and novel sensing mechanisms for signal transduction systems

“…The redox‐mediated modulation of sensor kinases by chemical modification of cysteine residues has also been observed for E. coli EvgS (Inada et al, 2021), P. putida TodS (Silva‐Jimenez et al, 2015), Azoarcus sp. AccS (Valderrama et al, 2019) and Staphylococcus aureus SrrB (Tiwari et al, 2020). The phylogenetic spread of these bacteria may indicate that this represents a more general mechanism.…”

Nitrate- and Nitrite-Sensing Histidine Kinases: Function, Structure, and Natural Diversity

“…Thus, it is possible that the previously observed dependence of NarQ activity on aeration [ 219 ] is achieved via formation of the disulfide bond in the catalytic domain. Overall, the regulation of protein activity by redox-sensitive cysteines is a common phenomenon, also among TCSs such as ArcBA, PrrBA, RegBA [ 220 , 221 ], or the recently discovered AccSR [ 222 ].…”

Genetic characterization of the cyclohexane carboxylate degradation pathway in the denitrifying bacterium Aromatoleum sp. CIB

“…CIB (Rabus et al, 2019 ; Raittz et al, 2021 ) is a facultative anaerobic β‐proteobacterium able to degrade either aerobically or anaerobically (denitrifying) a wide range of aromatic compounds. Under anoxic conditions most aromatic compounds are funnelled to the benzoyl‐CoA central intermediate that is converted to the aliphatic 3‐hydroxypimelyl‐CoA compound via the Bzd pathway encoded by the bzd cluster (Carmona et al, 2009 ; Durante‐Rodríguez et al, 2018 ; López‐Barragán et al, 2004 ; Valderrama et al, 2019 ) [Figure 1(B) ]. The strain CIB is also able to grow anaerobically using CHC as sole carbon and energy source (Blázquez et al, 2008 ).…”