Pn. Rather et al., AARC, AN ESSENTIAL GENE INVOLVED IN DENSITY-DEPENDENT REGULATION OF THE 2'-N-ACETYLTRANSFERASE IN PROVIDENCIA-STUARTII, Journal of bacteriology, 179(7), 1997, pp. 2267-2273
The 2'-N-acetyltransferase [AAC(2')-Ia] in Providencia stuartii has a
dual function where it is involved in the acetylation of peptidoglycan
and certain aminoglycosides, A search for negative regulators of the
aac(2')-Ia gene has resulted in the identification of aarC. A missense
allele (aarC1) resulted in an 8.9-fold increase in beta-galactosidase
accumulation from an aac(2')-lacZ transcriptional fusion. Northern bl
ot analysis demonstrated an increase in aac(2')-Ia mRNA accumulation t
hat was specific to cells at high density. In addition, the aarC1 alle
le also resulted in a substantial increase in the expression of aarP,
a transcriptional activator of the aac(2')-Ia gene. The wild-type aarC
gene was isolated by complementation and encodes a predicted protein
of 365 amino acids with a molecular mass of 39,815 Da. The predicted A
arC protein exhibited 88% amino acid homology to the previously identi
fied GcpE protein of Escherichia coli and 86% homology to a gene produ
ct from Haemophilus influenzae. The E. coli gcpE gene was able to func
tionally complement the aarC1 allele in P. stuartii. The aarC1 allele
was identified as a T to G transversion that resulted in a valine to g
lycine substitution at position 136 in the AarC protein. The aarC gene
appears to be essential for cell viability as construction of a disru
pted copy (aarC::lacZ) was possible only in cells that carried an epis
omal copy of aarC or gcpE.