The electrostatic core of the outer membrane protein X from E. coli

Area of Science:

• Molecular biophysics
• Protein structure and stability
• Membrane protein architecture

Background:

• Electrostatic side chain contacts significantly contribute to protein stability.
• The role of electrostatic interactions in outer membrane proteins is less understood than in soluble proteins.

Purpose of the Study:

• To systematically investigate the impact of charged side chains on the structure and stability of the E. coli outer membrane protein X (OmpX).
• To identify key electrostatic interactions contributing to OmpX stability in detergent micelles.

Main Methods:

• Systematic study of all charged side chains in OmpX.
• Analysis of electrostatic interactions within the protein core.
• Assessment of protein stability in dodecylphosphocholine (DPC) detergent micelles.

Main Results:

• Identification of three distinct salt-bridge clusters within the core of OmpX.
• These clusters significantly contribute to the stability of OmpX in DPC micelles.
• The identified clusters form an "electrostatic core," analogous to the hydrophobic core of soluble proteins.

Conclusions:

• Electrostatic interactions, particularly salt bridges, play a critical role in the structural architecture and stability of outer membrane proteins like OmpX.
• The concept of an "electrostatic core" provides a new framework for understanding membrane protein stability.