Evolved neomycin phosphotransferase from an isolate of Klebsiella pneumoniae.
A new aminoglycoside resistance gene (aphA1-IAB) confers high-level resistance to neomycin. The sequence of aphA1-IAB is closely related to aphA1 found in the transposons Tn4352, Tn903 and Tn602. For example, aphA1-IAB differs from aphA1-903 at five nucleotides that result in four amino acid replacements. The enzyme encoded by aphA1-IAB has a significantly higher turnover number with neomycin, kanamycin and G418 as substrates than does the aphA1-903 enzyme. A parsimonious phylogenetic tree suggests that aphA1-IAB evolved from an ancestral form that is closely related or identical to the aphA1 found in Tn903. The excess of replacement substitutions over silent substitutions in aphA1-IAB, as well as its convergence toward aphA3 from Staphylococcus aureus, is indicative of selective evolution. Our hypothesis to explain these results is that aphA1-IAB evolved under the selective pressure of neomycin use in relatively recent times.
Lee
K Y
KY
Department of Medical Microbiology and Immunology, School of Medicine, University of California, Davis 95616.
Hopkins
J D
JD
Syvanen
M
M
D000595:Amino Acid Sequence; D001483:Base Sequence; D005075:Biological Evolution; D015153:Blotting, Western; D004251:DNA Transposable Elements / Q000235:genetics; D004352:Drug Resistance, Microbial; D007612:Kanamycin / Q000378:metabolism / Q000494:pharmacology; D019868:Kanamycin Kinase; D007700:Kinetics; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D009355:Neomycin / Q000378:metabolism* / Q000494:pharmacology; D010770:Phosphotransferases / Q000737:chemistry / Q000235:genetics*; D010957:Plasmids / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D013211:Staphylococcus aureus / Q000235:genetics; D013696:Temperature
D004251:DNA Transposable Elements; D007612:Kanamycin; D010770:Phosphotransferases; D019868:Kanamycin Kinase; D009355:Neomycin