Dynamic signature of activity-stability tradeoff in lactamase evolution

TL;DR

The study reveals how TEM-1 β-lactamase evolves resistance to cefotaxime by balancing enzyme activity and stability through dynamic structural changes.

Contribution

The paper introduces a novel framework for understanding how protein evolution balances activity and stability via conformational ensembles and localized stability networks.

Findings

Initial mutations in β-lactamase reorganize the active site and introduce new functional conformations.

Stabilizing substitutions restore populations of original conformations rather than stabilizing new ones.

Stability defects are clustered at distal scaffold elements, enabling conformational epistasis and compensatory states.

Abstract

Our ability to understand protein evolution hinges on understanding how evolutionary landscapes are shaped at the fundamental protein level. Using TEM-1 β-lactamase we show that molecular traits related to the statistical ensemble nature of protein structure contribute to broader substrate specificity, active site-scaffold communication, and the selection of stabilizing substitutions. During the evolution of cefotaxime resistance, the initial mutation reorganizes the active site, introducing a new function conformation. Secondary substitutions improve catalytic efficiency by redistributing the ensemble and restoring a significant population of the original conformation, rather than by stabilizing the new conformation. Stability defects associated with initial mutations are not evenly disseminated but are clustered at specific distal scaffold elements. The capacity of mutants to independently modulate the populations of individual active site walls and scaffold regions through narrow residue networks, produces conformational epistasis and a combinatorial set of cefotaximase states, which enables local compensation of scaffold defects.

Enzymes adapt by sampling new conformations while balancing destabilizing effects of mutations. Here, the authors reveal how TEM-1 β-lactamase acquires cefotaxime resistance through reshaping of dynamic conformational ensembles and localized stability networks, offering insight into the molecular framework of the activity-stability tradeoff.

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