Analysis of fast channel blockage: revealing substrate binding in the microsecond range

Area of Science:

• Microbiology
• Biophysics
• Pharmacology

Background:

• Antibiotics must cross bacterial outer membranes via porin channels to be effective.
• Hydrophilic antibiotics like β-lactams utilize porins to enter the periplasm.
• Electrophysiology, noise analysis, and single event analysis are current methods to study antibiotic-porin interactions.

Purpose of the Study:

• To develop a novel framework for analyzing ion-current noise with enhanced time resolution.
• To enable the study of fast binding events and incomplete channel blockages by substrates.
• To investigate the interaction between the antibiotic meropenem and the OmpF porin.

Main Methods:

• A new framework for ion-current noise analysis incorporating analogous filter and sampling corrections.
• Application of the method to study meropenem-OmpF porin interactions in Escherichia coli.
• Estimation of binding kinetics (on and off rates) from ion current and power spectral density.

Main Results:

• The novel method achieves extended time resolution, surpassing limitations of previous techniques.
• Fast binding events and partial channel blockages can be analyzed.
• The average residence time of meropenem within the OmpF porin was determined to be in the microseconds range.

Conclusions:

• The developed noise analysis framework offers a powerful tool for studying rapid molecular interactions at the single-channel level.
• This method provides new insights into antibiotic transport mechanisms across bacterial membranes.
• Understanding these interactions is crucial for developing more effective antibiotics.