IDENTIFICATION AND CHARACTERIZATION OF AARF, A LOCUS REQUIRED FOR PRODUCTION OF UBIQUINONE IN PROVIDENCIA STUARTII AND ESCHERICHIA-COLI ANDFOR EXPRESSION OF 2'-N-ACETYLTRANSFERASE IN PROVIDENCIA-STUARTII

Providencia stuartii contains a chromosomal 2'-N-acetyltransferase [AA C(2')-Ia] involved in the O acetylation of peptidoglycan. The AAC(2')- Ia enzyme is also capable of acetylating and inactivating certain amin oglycosides and confers high-level resistance to these antibiotics whe n overexpressed. We report the identification of a locus in P. stuarti i, designated aarF, that is required for the expression of AAC(2')-Ia. Northern (RNA) analysis demonstrated that aac(2')-Ia mRNA levels were dramatically decreased in a P. stuartii strain carrying an aarF:Cm di sruption, The aarF::Cm disruption also resulted in a deficiency in the respiratory cofactor ubiquinone, The aarF locus encoded a protein tha t had a predicted molecular mass of 62,559 Da and that exhibited exten sive amino acid similarity to the products of two adjacent open readin g frames of unknown function (YigQ and YigR), located at 86 min on the Escherichia coli chromosome. An E. coli yigR::Kan mutant was also def icient in ubiquinone content. complementation studies demonstrated tha t the aarF and the E. coli yigQR loci were functionally equivalent. Th e aarF or yigQR genes were unable to complement ubiD and ubiE mutation s that are also present at 86 min on the E. coli chromosome, This resu lt indicates that aarF (yigQR) represents a novel locus for ubiquinone production and reveals a previously unreported connection between ubi quinone biosynthesis and the regulation of gene expression.