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Published on: January 5, 2024
Mechanistic plasticity in ApmA enables aminoglycoside promiscuity for resistance
Emily Bordeleau1, Peter J Stogios2, Elena Evdokimova2
1David Braley Centre for Antibiotics Discovery, M.G. DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
Abstract:
The efficacy of aminoglycoside antibiotics is waning due to the acquisition of diverse resistance mechanisms by bacteria. Among the most prevalent are aminoglycoside acetyltransferases (AACs) that inactivate the antibiotics through acetyl coenzyme A-mediated modification. Most AACs are members of the GCN5 superfamily of acyltransferases which lack conserved active site residues that participate in catalysis. ApmA is the first reported AAC belonging to the left-handed β-helix superfamily. These enzymes are characterized by an essential active site histidine that acts as an active site base. Here we show that ApmA confers broad-spectrum aminoglycoside resistance with a molecular mechanism that diverges from other detoxifying left-handed β-helix superfamily enzymes and canonical GCN5 AACs. We find that the active site histidine plays different functions depending on the acetyl-accepting aminoglycoside substrate. This flexibility in the mechanism of a single enzyme underscores the plasticity of antibiotic resistance elements to co-opt protein catalysts in the evolution of drug detoxification.
Insights
A novel enzyme, ApmA, provides broad-spectrum aminoglycoside antibiotic resistance. Its unique mechanism, utilizing a flexible active site histidine, differs from other resistance enzymes, highlighting the adaptability of bacterial resistance strategies.
Area of Science:
- Microbiology
- Biochemistry
- Structural Biology
Background:
- Bacterial resistance to aminoglycoside antibiotics is a growing global health concern.
- Aminoglycoside acetyltransferases (AACs) are key enzymes conferring resistance by inactivating antibiotics.
- Most known AACs belong to the GCN5 superfamily, lacking conserved catalytic residues.
Purpose of the Study:
- To characterize the novel aminoglycoside acetyltransferase ApmA, the first reported from the left-handed β-helix superfamily.
- To elucidate the molecular mechanism of ApmA-mediated aminoglycoside resistance.
- To compare ApmA's mechanism with other AACs and left-handed β-helix enzymes.
Main Methods:
- Biochemical assays to determine enzyme activity and substrate specificity.
- Structural analysis to understand active site architecture.
- Comparative analysis with known aminoglycoside acetyltransferases and left-handed β-helix enzymes.
Main Results:
- ApmA confers broad-spectrum aminoglycoside resistance.
- ApmA's catalytic mechanism diverges significantly from other detoxifying left-handed β-helix enzymes and GCN5 AACs.
- The active site histidine in ApmA exhibits substrate-dependent functional flexibility.
Conclusions:
- ApmA represents a novel class of aminoglycoside resistance enzymes with a unique catalytic mechanism.
- The plasticity of antibiotic resistance elements is demonstrated by ApmA's ability to co-opt protein catalysts for drug detoxification.
- Understanding ApmA's mechanism provides insights into the evolution of antibiotic resistance.
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