A Selective Tether Recruits Activated Response Regulator CheB to Its Chemoreceptor Substrate.

Area of Science:

• Microbiology and Molecular Biology
• Biochemistry and Biophysics

Background:

• Two-component signal transduction systems enable bacteria to sense and respond to environmental cues.
• Response regulators, like CheB (methylesterase/deamidase), are crucial components, often acting as enzymes.
• CheB activation involves phosphorylation and interaction with chemoreceptor pentapeptide motifs.

Purpose of the Study:

• To investigate the interplay between CheB phosphorylation, pentapeptide binding, and substrate interaction.
• To elucidate the mechanism of CheB regulation by its chemoreceptor target.

Main Methods:

• Characterization of binding kinetics of CheB to Nanodisc-inserted chemoreceptor dimers.
• Utilized a phosphorylation mimic to assess its effect on pentapeptide binding.
• Employed molecular modeling to predict the pentapeptide-binding site on CheB.

Main Results:

• A synergistic relationship was observed between CheB phosphorylation and pentapeptide binding.
• Phosphorylation mimic enhanced pentapeptide binding, with the pentapeptide acting as a high-affinity tether.
• The pentapeptide selectively binds phosphorylated CheB, stabilizing its active conformation.

Conclusions:

• CheB activation is regulated by a novel mechanism involving selective tethering of the activated enzyme by its target.
• Chemoreceptor pentapeptides act as selective tethers, recruiting and stabilizing the active conformation of CheB.
• This highlights an active role for target molecules in regulating response regulator activity, a potentially widespread strategy in bacterial signaling.