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Biology subjects

Lund, B. A.

Publications and source records attributed to Lund, B. A..

2 recordsLinked to original sources

Biophysical characterization and analysis of a mesophilic chorismate mutase from B. pumilus

Chorismate mutases have extensively been used as computational benchmarking systems for enzyme catalysis, yet the roles entropy and enthalpy play in catalysis are still not fully understood. Thus, it is important to better understand these enzymes for potential research or industrial applications. Here, we report the first crystal structure and kinetic characterization of a chorismate mutase from Bacillus pumilus. This enzyme exhibits a high degree of similarity to a known mesophilic chorismate mutase from Bacillus subtilis. Using this crystal structure, we further employ EVB/MD simulations to construct Arrhenius plots, allowing us to extract thermodynamic activation parameters. Overall, this study provides new insights into the structural and functional features of the B. pumilus chorismate mutase and highlights its potential as a valuable enzyme for biocatalytic and biotechnological applications.

biochemistry↗

Cryptic β-lactamase evolution is driven by low β-lactam concentrations

Our current understanding of how low antibiotic concentrations shape the evolution of contemporary {beta}-lactamases is limited. Using the wide-spread carbapenemase OXA-48, we tested the long-standing hypothesis that selective compartments with low antibiotic concentrations cause standing genetic diversity that could act as a gateway to develop clinical resistance. Here, we subjected Escherichia coli expressing blaOXA-48, on a clinical plasmid, to experimental evolution at sub-minimum inhibitory concentrations (sub-MIC) of ceftazidime. We identified and characterized seven single variants of OXA-48. Susceptibility profiles and dose-response curves showed that they increased resistance only marginally. However, in competition experiments at sub-MIC of ceftazidime, they showed strong selectable fitness benefits. Increased resistance was also reflected in elevated catalytic efficiencies towards ceftazidime. These changes are likely caused by enhanced flexibility of the {Omega}- and {beta}5-{beta}6 loops. In conclusion, low-level concentrations of {beta}-lactams can drive the evolution of {beta}-lactamases through cryptic phenotypes which may act as stepping-stones towards clinical resistance.

evolutionary biology↗