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J. Bacteriol., 05 1997, 2892-2899, Vol 179, No. 9
M Reddy and J Gowrishankar
A Lac+ papillation assay was used to identify mutants (tex) of Escherichia
coli that exhibit an increased frequency of precise excision of a
lacZ::Tn10dKan insertion. Three tex strains had suffered mutations in the
gene (ssb) encoding the essential single-stranded DNA- binding protein SSB,
which resulted in the following alterations in the 177-residue protein:
G4D; L10F, P24S; and V102M. The phenotypes of these ssb mutants indicated
that they were largely unaffected in other functions mediated by SSB, such
as DNA replication, recombination, and repair. Strains with multicopy ssb+
exhibited a decreased frequency of Tn10dKan precise excision. Three other
tex mutants had insertion mutations in the locus designated uup at 21.75
min on the linkage map. The nucleotide sequence of uup was determined, and
the gene was inferred to encode a 625-amino-acid hydrophilic protein that
belongs to the superfamily of ABC-domain proteins (with two pairs of the
Walker A and B motifs), which are postulated to be involved in coupling ATP
hydrolysis with other biological processes. The uup gene product shares
extensive homology with the deduced sequences of two proteins of
Haemophilus influenzae. The uup gene is also situated immediately upstream
of (and is transcribed in the same direction as) the paraquat- inducible
SoxRS-regulated pqi-5 gene, two reported promoters for which are situated
within the uup coding sequence.
Copyright © 1997, American Society for Microbiology
Identification and characterization of ssb and uup mutants with increased frequency of precise excision of transposon Tn10 derivatives: nucleotide sequence of uup in Escherichia coli
Centre for Cellular & Molecular Biology, Hyderabad, India.
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