The aminoglycoside 6'-N-acetyltransferase type Ib encoded by Tn1331 is evenly distributed within the cell's cytoplasm.
The multiresistance transposon Tn1331, which mediates resistance to several aminoglycosides and beta-lactams, includes the aac(6')-Ib, aadA1, bla(OXA-9), and bla(TEM-1) genes. The nucleotide sequence of aac(6')-Ib includes a region identical to that of the bla(TEM-1) gene. This region encompasses the promoter and the initiation codon followed by 15 nucleotides. Since there were three possible translation initiation sites, the amino acid sequence at the N terminus of the aminoglycoside 6'-N-acetyltransferase type Ib [AAC(6')-Ib] was determined and was found to be SIQHF. This result indicated that aac(6')-Ib includes a translational fusion: the first five amino acids of the leader peptide of the TEM beta-lactamase are fused to the rest of the AAC(6')-Ib protein. This gene fusion could have formed during the genesis of Tn1331 as a consequence of the generation of a 520-nucleotide duplication (M. E. Tolmasky, Plasmid 24:218-226, 1990). An identical gene isolated from a Serratia marcescens strain has been previously described (G. Tran van Nhieu and E. Collatz, J. Bacteriol. 169:5708-5714, 1987). Extraction of the periplasmic proteins of E. coli harboring aac(6')-Ib by spheroplast formation showed that most of the AAC(6')-Ib protein is present in the cytoplasm. A genetic fusion to phoA confirmed these results. AAC(6')-Ib was shown to be evenly distributed inside the cell's cytoplasm by fluorescent microscopy with an AAC(6')-Ib-cyan fluorescent protein fusion.
Dery
Ken J
KJ
Department of Biological Science, College of Natural Science and Mathematics, California State University Fullerton, Fullerton, California 92834-6850, USA.
Søballe
Britta
B
Witherspoon
Mavee S L
MS
Bui
Duyen
D
Koch
Robert
R
Sherratt
David J
DJ
Tolmasky
Marcelo E
ME
D000123:Acetyltransferases / Q000235:genetics*; D000469:Alkaline Phosphatase / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D003593:Cytoplasm / Q000201:enzymology*; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology*; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D013347:Subcellular Fractions / Q000201:enzymology
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D000123:Acetyltransferases; C056532:aminoglycoside N(6')-acetyltransferase; D000469:Alkaline Phosphatase