Multiple signals modulate the activity of the complex sensor kinase TodS

Area of Science:

• Microbiology
• Biochemistry
• Molecular Biology

Background:

• Complex sensor kinases integrate diverse environmental signals for cellular regulation.
• The sensor kinase TodS and response regulator TodT control toluene metabolism in Pseudomonas putida.
• Previous studies indicated TodS responds to aromatic hydrocarbons as agonists or antagonists.

Purpose of the Study:

• To investigate the response of TodS to oxidative agents.
• To elucidate the mechanism by which menadione affects TodS activity.
• To understand the interplay between menadione and toluene signaling in metabolic regulation.

Main Methods:

• In vitro enzyme activity assays to measure TodS autophosphorylation.
• In vivo studies measuring the expression of the PtodX gene.
• Site-directed mutagenesis of the conserved cysteine residue (C320) in TodS.

Main Results:

• Menadione, an oxidative agent, was identified as an inhibitor of TodS activity.
• Menadione inhibited TodS in vitro and reduced PtodX expression in vivo, a cysteine-dependent process.
• Mutating the sole conserved cysteine (C320) abolished menadione sensitivity.
• Menadione antagonized toluene's effect on TodS activity, suggesting interwoven regulation.

Conclusions:

• TodS integrates oxidative stress signals (menadione) with hydrocarbon signals (toluene).
• The cysteine-dependent mechanism of menadione sensing provides mechanistic insight into signal integration.
• This cross-regulation between glucose and toluene metabolism highlights the complexity of microbial metabolic networks.