Analysis of the self-defense gene (fmrO) of a fortimicin A (astromicin) producer, Micromonospora olivasterospora: comparison with other aminoglycoside-resistance-encoding genes.
The nucleotide (nt) sequence of a 3409-bp PvuII fragment carrying the self-defense gene (fmrO) of a fortimicin A (FmA; astromicin) producer, Micromonospora olivasterospora, was determined; four open reading frames (ORFs) exist in this region. Expression analysis of fmrO using the lac promoter in Escherichia coli revealed that ORF-3 encodes fmrO. ORF-1 was considered to encode a FmKH epimerase (fms11). ORF-2, ORF-3 and ORF-4 seemed to form an operon. No homology was detected between fmrO and the resistance-encoding gene fmrT of Streptomyces tenjimariensis, a producer of the Fm-group antibiotic, istamycin. Gene organization around the fmr genes differed considerably between M. olivasterospora and S. tenjimariensis. The deduced amino acid sequence of fmrO showed an identity of 30.8% to grmA of M. purpurea and 35.8% to grmB of M. rosea, respectively, suggesting that fmrO encodes a 16S rRNA methyltransferase. We found in M. purpurea a novel resistance gene distinct from grmA and highly similar to fmrO which conferred a resistance phenotype similar to that of fmrO. These results suggest that fmrO of M. olivasterospora and the two resistance-encoding genes of M. purpurea were derived from a common ancestral gene.
Ohta
T
T
Tokyo Research Laboratories, Kyowa Hakko Kogyo Co., Ltd., Japan.
Hasegawa
M
M
D000595:Amino Acid Sequence; D000617:Aminoglycosides; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D004269:DNA, Bacterial; D004352:Drug Resistance, Microbial / Q000235:genetics; D005798:Genes, Bacterial; D006801:Humans; D007231:Infant, Newborn; D008780:Methyltransferases / Q000235:genetics; D008847:Micromonospora / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; C023384:fortimicin A; D008780:Methyltransferases