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Functional and Structural Characterization of Acquired 16S rRNA Methyltransferase NpmB1 Conferring Pan-Aminoglycoside
Akito Kawai1, Masahiro Suzuki1, Kentaro Tsukamoto1
1Department of Microbiology, Fujita Health Universitygrid.256115.4 School of Medicine, Aichi, Japan.
Abstract:
Posttranslational methylation of the A site of 16S rRNA at position A1408 leads to pan-aminoglycoside resistance encompassing both 4,5- and 4,6-disubstituted 2-deoxystreptamine (DOS) aminoglycosides. To date, NpmA is the only acquired enzyme with such a function. Here, we present the function and structure of NpmB1, whose sequence was identified in Escherichia coli genomes registered from the United Kingdom. NpmB1 possesses 40% amino acid identity with NpmA1 and confers resistance to all clinically relevant aminoglycosides, including 4,5-DOS agents. Phylogenetic analysis of NpmB1 and NpmB2, its single-amino-acid variant, revealed that the encoding gene was likely acquired by E. coli from a soil bacterium. The structure of NpmB1 suggests that it requires a structural change of the β6/7 linker in order to bind to 16S rRNA. These findings establish NpmB1 and NpmB2 as the second group of acquired pan-aminoglycoside resistance 16S rRNA methyltransferases.
Insights
A newly discovered enzyme, NpmB1, found in Escherichia coli, provides pan-aminoglycoside resistance by methylating 16S rRNA. This enzyme, along with its variant NpmB2, represents a second class of acquired resistance methyltransferases.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Posttranslational methylation of 16S rRNA at A1408 confers pan-aminoglycoside resistance.
- NpmA is the only previously identified acquired enzyme with this resistance function.
- Aminoglycosides are crucial antibiotics, and resistance mechanisms pose a significant threat to public health.
Purpose of the Study:
- To characterize the function and structure of a newly identified enzyme, NpmB1, from Escherichia coli.
- To determine the resistance profile conferred by NpmB1 and its variant, NpmB2.
- To investigate the evolutionary origins of the NpmB genes.
Main Methods:
- Sequence analysis and identification of NpmB1 in Escherichia coli genomes.
- Biochemical assays to determine the methyltransferase activity and resistance profile of NpmB1.
- Structural analysis of NpmB1 to understand its mechanism of action.
- Phylogenetic analysis to trace the evolutionary history of NpmB genes.
Main Results:
- NpmB1 confers resistance to all clinically relevant aminoglycosides, including 4,5-disubstituted 2-deoxystreptamine (DOS) agents.
- NpmB1 shares 40% amino acid identity with NpmA1 and exhibits similar pan-aminoglycoside resistance.
- Phylogenetic analysis suggests NpmB genes were acquired by E. coli from soil bacteria.
- Structural insights indicate NpmB1 requires conformational changes for 16S rRNA binding.
Conclusions:
- NpmB1 and NpmB2 represent a second distinct group of acquired 16S rRNA methyltransferases conferring pan-aminoglycoside resistance.
- The discovery of NpmB1 expands our understanding of aminoglycoside resistance mechanisms.
- These findings highlight the ongoing evolution of antibiotic resistance in bacteria and the potential for novel resistance enzymes to emerge.
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