A feed-forward loop guarantees robust behavior in Escherichia coli carbohydrate uptake.

Area of Science:

• Microbial physiology
• Systems biology
• Biochemical modeling

Background:

• The phosphoenolpyruvate: carbohydrate phosphotransferase system (PTS) in Escherichia coli functions as a sensor for glycolytic flux.
• The output of this sensor, phosphorylated EIIA, influences the global transcription factor Crp, impacting cellular behavior.
• Understanding the kinetic and structural properties of the PTS is crucial for comprehending cellular regulation.

Purpose of the Study:

• To develop and analyze a family of mathematical models for the PTS in Escherichia coli.
• To investigate the robustness of the PTS in measuring glycolytic flux across varying model complexities.
• To elucidate the mechanisms underlying the system's structural and quantitative robustness.

Main Methods:

• Development of a series of mathematical models with increasing complexity.
• Simulation of models using MATLAB.
• Analysis of model behavior in response to variations in experimental data and parameters.
• Identification of key regulatory elements contributing to system robustness.

Main Results:

• A family of mathematical models exhibiting robust behavior was presented.
• The models successfully described experimental data relating PTS output to specific growth rate.
• A feed-forward loop involving pyruvate kinase activation by an upper glycolysis metabolite was identified as key to robustness.
• Robustness was demonstrated across variations in measured data and model parameters.

Conclusions:

• The phosphoenolpyruvate: carbohydrate phosphotransferase system in Escherichia coli exhibits robust control over glycolytic flux measurement.
• A feed-forward loop within glycolysis is a critical determinant of this robustness.
• Mathematical modeling provides valuable insights into the complex regulatory mechanisms of microbial metabolism.