An extracellular factor regulating expression of the chromosomal aminoglycoside 2'-N-acetyltransferase of Providencia stuartii.
The chromosomal aac(2')-Ia gene in Providencia stuartii encodes a housekeeping 2'-N-acetyltransferase [AAC(2')-Ia] involved in the acetylation of peptidoglycan. In addition, the AAC(2')-Ia enzyme also acetylates and confers resistance to the clinically important aminoglycoside antibiotics gentamicin, tobramycin, and netilmicin. Expression of the aac(2')-Ia gene was found to be strongly influenced by cell density, with a sharp decrease in aac(2')-Ia mRNA accumulation as cells approached stationary phase. This decrease was mediated by the accumulation of an extracellular factor, designated AR (for acetyltransferase repressing)-factor. AR-factor was produced in both minimal and rich media and acted in a manner that was strongly dose dependent. The activity of AR-factor was also pH dependent, with optimal activity at pH 8.0 and above. Biochemical characterization of conditioned media from P. stuartii has shown that AR-factor is between 500 and 1,000 Da in molecular size and is heat stable. In addition, AR-factor was inactivated by a variety of proteases, suggesting that it may be a small peptide.
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Department of Medicine, Case Western Reserve University School of Medicine, Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA. pxr17@po.cwru.edu
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D000123:Acetyltransferases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D005798:Genes, Bacterial; D011532:Providencia / Q000201:enzymology* / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*
D012333:RNA, Messenger; D012097:Repressor Proteins; D000123:Acetyltransferases; C443113:aminoglycoside 2'-N-acetyltransferase