An antibiotic-resistance conferring mutation in a neisserial porin: Structure, ion flux, and ampicillin binding

Area of Science:

• Microbiology
• Structural Biology
• Biophysics

Background:

• Gram-negative bacteria are responsible for most highly drug-resistant infections.
• Antibiotics must pass through porin channels in the outer membrane to reach their targets.
• Porin mutations are a known mechanism for developing antibiotic resistance.

Purpose of the Study:

• To investigate how a single point mutation in the Neisseria meningitidis PorB porin affects beta-lactam antibiotic interaction.
• To elucidate the molecular mechanisms underlying porin-mediated antibiotic resistance in Gram-negative bacteria.

Main Methods:

• X-ray crystallography to determine structural changes.
• High-resolution electrophysiology to measure ion and drug flow.
• Atomistic biomolecular simulations to model drug-porin interactions.
• Liposome swelling assays to assess drug permeation.

Main Results:

• A single point mutation in PorB alters drug binding affinity and ion selectivity.
• The mutation affects the permeability of beta-lactam antibiotics through the porin channel.
• Distinct interactions between the porin's electric field and zwitterionic drugs were observed, influenced by the mutation.

Conclusions:

• Porin mutations play a critical role in antibiotic resistance by modulating drug permeation.
• Understanding these drug-porin interactions is crucial for developing new strategies against resistant Gram-negative infections.
• The findings offer insights into broader drug-channel interactions and resistance mechanisms.