Novel plasmid-mediated 16S rRNA m1A1408 methyltransferase, NpmA, found in a clinically isolated Escherichia coli strain resistant to structurally diverse aminoglycosides.
We have isolated a multiple-aminoglycoside-resistant Escherichia coli strain, strain ARS3, and have been the first to identify a novel plasmid-mediated 16S rRNA methyltransferase, NpmA. This new enzyme shared a relatively low level of identity (30%) to the chromosomally encoded 16S rRNA methyltransferase (KamA) of Streptomyces tenjimariensis, an actinomycete aminoglycoside producer. The introduction of a recombinant plasmid carrying npmA could confer on E. coli consistent resistance to both 4,6-disubstituted 2-deoxystreptamines, such as amikacin and gentamicin, and 4,5-disubstituted 2-deoxystreptamines, including neomycin and ribostamycin. The histidine-tagged NpmA elucidated methyltransferase activity against 30S ribosomal subunits but not against 50S subunits and the naked 16S rRNA molecule in vitro. We further confirmed that NpmA is an adenine N-1 methyltransferase specific for the A1408 position at the A site of 16S rRNA. Drug footprinting data indicated that binding of aminoglycosides to the target site was apparently interrupted by methylation at the A1408 position. These observations demonstrate that NpmA is a novel plasmid-mediated 16S rRNA methyltransferase that provides a panaminoglycoside-resistant nature through interference with the binding of aminoglycosides toward the A site of 16S rRNA through N-1 methylation at position A1408.
Wachino
Jun-ichi
J
Department of Bacterial Pathogenesis and Infection Control, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashi-Murayama, Tokyo 208-0011, Japan.
Shibayama
Keigo
K
Kurokawa
Hiroshi
H
Kimura
Kouji
K
Yamane
Kunikazu
K
Suzuki
Satowa
S
Shibata
Naohiro
N
Ike
Yasuyoshi
Y
Arakawa
Yoshichika
Y
D000595:Amino Acid Sequence; D000617:Aminoglycosides / Q000737:chemistry / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008780:Methyltransferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D011485:Protein Binding; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000378:metabolism; D054679:Ribosome Subunits, Small / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D012336:RNA, Ribosomal, 16S; D008780:Methyltransferases; C554940:NpmA protein, E coli