The region of the IncN plasmid R46 coding for resistance to beta-lactam antibiotics, streptomycin/spectinomycin and sulphonamides is closely related to antibiotic resistance segments found in IncW plasmids and in Tn21-like transposons.
The nucleotide sequence of a 2.5 kb segment of the pKM101 (R46) genome has been determined. The 1.3 kb from a BamHI site at 153 to base 1440 differs by only 2 bases from a part of the published sequence of the aadB (gentamicin resistance) gene region including the coding region for the N-terminal 70 amino acids of the predicted aadB product. The same sequence has been found 5'-to the dhfrII gene of R388 and to the aadA gene of Tn21 (R538-1). Three open reading frames are located in this region, two on the same strand as the resistance genes and one on the complementary strand. The latter predicts a polypeptide of 337 amino acids, whose N-terminal segment is 40% homologous to the predicted product of an open reading frame of 179 amino acids located next to the dhfrI gene of Tn7. The oxa2 (oxacillin resistance) gene predicts a long polypeptide commencing with (the N-terminal) 70 amino acids of the aadB product. A similar arrangement is found in the aadA gene of R538-1. The N-terminal segment of an aadA gene is located 3'- to oxa2, separated by 36 bases. Sequences surrounding the BamHI site are identical to sequences 5'- to the tnpM gene of Tn21 and homology ceases where homology between Tn21 and Tn501 commences. The possibility that this antibiotic resistance segment is a discrete mobile DNA element is discussed.
Hall
R M
RM
CSIRO Division of Molecular Biology, North Ryde, NSW, Australia.
Vockler
C
C
D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001483:Base Sequence; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D008969:Molecular Sequence Data; D011815:R Factors; D012689:Sequence Homology, Nucleic Acid; D000198:Spectinomycin / Q000494:pharmacology; D013307:Streptomycin / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D013449:Sulfonamides; D047090:beta-Lactams; D000198:Spectinomycin; D013307:Streptomycin