Cd. Lu et al., IDENTIFICATION OF GREA ENCODING A TRANSCRIPTIONAL ELONGATION-FACTOR AS A MEMBER OF THE CARA-ORF-CARB-GREA OPERON IN PSEUDOMONAS-AERUGINOSA PAO1, Journal of bacteriology, 179(9), 1997, pp. 3043-3046
A homolog of the transcriptional elongation factor, GreA, was identifi
ed in Pseudomonas aeruginosa PAO1. The deduced amino acid sequence for
GreA from this organism exhibits 65.2% identity to its counterpart in
Escherichia coli K-12. The nucleotide sequence of greA from P. aerugi
nosa overlaps by four bases the 3' terminus of carB which encodes the
large subunit of carbamoylphosphate synthetase. S1 nuclease experiment
s showed that level of the greA transcript is elevated approximately 1
0-fold under conditions of pyrimidine limitation, consistent with the
conclusion that transcription is initiated from the previously identif
ied pyrimidine-sensitive promoter upstream of the carA-orf-carB-greA o
peron. Transcriptional fusion experiments showed the presence of an ad
ditional weak promoter within the carB sequence. A greA insertional mu
tant of Pseudomonas aerugionsa was constructed by gene replacement. Th
e mutant derivative grew well in rich medium but did not grow in minim
al medium supplemented by arginine and nucleosides. The greA phenotype
was suppressed by secondary mutations at a relatively high rate, cons
istent,vith the notion of an important physiological role for GreA.