An allosteric model for control of pore opening by substrate binding in the EutL microcompartment shell protein

Area of Science:

• Bacterial microcompartments
• Protein structure and function
• Metabolic engineering

Background:

• Ethanolamine utilization (Eut) microcompartments are protein-based organelles crucial for bacterial metabolism and pathogenesis.
• Their protein shell regulates substrate and cofactor passage, but the mechanism for selective permeability is unclear.
• EutL, a shell protein, exhibits conformational changes suggesting a gated pore for cofactor transport.

Purpose of the Study:

• To elucidate the mechanism by which the Eut microcompartment shell regulates molecule transport.
• To investigate the role of ethanolamine and its binding to EutL in controlling pore permeability.
• To propose a new model for EutL function based on structural and biophysical evidence.

Main Methods:

• X-ray crystallography of EutL from Clostridium perfringens in various states.
• Equilibrium binding studies to determine ethanolamine interaction with EutL.
• Biophysical analyses to assess pore dynamics and allosteric regulation.

Main Results:

• Ethanolamine binds to EutL at a specific site present only in the closed-pore conformation.
• This binding acts as a negative allosteric regulator, preventing pore opening required for cofactor transport.
• Structural data reveals a mechanism consistent with the selective permeability of the Eut microcompartment.

Conclusions:

• Ethanolamine directly regulates EutL pore function through allosteric inhibition, controlling microcompartment permeability.
• This mechanism ensures efficient Eut microcompartment function by preventing premature cofactor release.
• Potential for redox modulation of this allosteric mechanism suggests new avenues for research.