Capturing the mutational landscape of the beta-lactamase TEM-1

Area of Science:

• Evolutionary Biology
• Biochemistry
• Genetics

Background:

• Adaptation relies on mutations, making their fitness effects crucial for predicting evolutionary trajectories.
• The distribution of mutant fitness effects (dMFE) and the forces shaping it are central to understanding organismal evolution and enzyme function.
• Antibiotic resistance, driven by enzymes like beta-lactamase TEM-1, poses a significant public health challenge.

Purpose of the Study:

• To explore the mutational landscape of the beta-lactamase TEM-1 enzyme.
• To identify key factors determining the impact of mutations on enzyme activity and antibiotic resistance.
• To develop a framework for studying mutation effects and epistatic interactions.

Main Methods:

• Generated and sequenced 10,000 mutants of beta-lactamase TEM-1.
• Assessed amoxicillin minimum inhibitory concentration (MIC) for 990 unique missense mutants.
• Analyzed mutation type, residue solvent accessibility, and predicted protein stability effects.

Main Results:

• Mutation type, residue solvent accessibility, and predicted stability changes were primary determinants of MIC.
• A single stabilizing mutation (M182T) significantly altered the enzyme's mutational landscape.
• A model of protein stability successfully captured the modification of the mutational landscape.

Conclusions:

• Mutation effects on enzyme activity are predictable based on intrinsic properties and stability.
• Understanding these factors is crucial for predicting evolutionary adaptation and the spread of antibiotic resistance.
• This study provides a framework for analyzing mutation effects and epistatic interactions in enzymes.