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J. Bacteriol., 12 1996, 6968-6974, Vol 178, No. 23
R Cavicchioli, T Kolesnikow, RC Chiang and RP Gunsalus
Analysis of the DNA sequence upstream of the narQ gene, which encodes the
second nitrate-responsive sensor-transmitter protein in Escherichia coli,
revealed an open reading frame (ORF) whose product shows a high degree of
similarity to a number of iron-sulfur proteins as well as to the beta
subunit of glutamate synthase (gltD) of E. coli. This ORF, located at 53.0
min on the E. coli chromosome, is divergently transcribed and is separated
by 206 bp from the narQ gene. Because of the small size of the intergenic
region, we reasoned that the genes may be of related function and/or
regulated in a similar fashion. An aegA- lacZ gene fusion was constructed
and examined in vivo; aegA expression was induced 11-fold by anaerobiosis
and repressed 5-fold by nitrate. This control was mediated by the fnr,
narX, narQ, and narL gene products. Analysis of an aegA mutant indicated
that the aegA gene product is not essential for cell respiration or
fermentation or for the utilization of ammonium or the amino acids
L-alanine, L-arginine, L- glutamic acid, glycine, and DL-serine as sole
nitrogen sources. The ORF was designated aegA to reflect that it is an
anaerobically expressed gene. The structural properties of the predicted
AegA amino acid sequence and the regulation of aegA are discussed with
regard to the possible function of aegA in E. coli.
Copyright © 1996, American Society for Microbiology
Characterization of the aegA locus of Escherichia coli: control of gene expression in response to anaerobiosis and nitrate
Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90095-1489, USA.
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