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

A Lac(+) papillation assay was used to identify mutants (tex) of Esche richia 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 p rotein SSB, which resulted in the following alterations in the 177-res idue protein: G4D; L10F, P24S; and V102M. The phenotypes of these sst, mutants indicated that they were largely unaffected in other function s mediated bq SSB, such as DNA replication, recombination, and repair, Strains with multicopy ssb(+) exhibited a decreased frequency of Tn10 dKan precise excision, Three other tex mutants had insertion mutations in the locus designated uup at 21.75 mill on the linkage map. The nuc leotide sequence of uup was determined, and the gene was inferred to e ncode a 625-amino-acid hydrophilic protein that belongs to the superfa mily of ABC-domain proteins (with two pairs of the Walker A and B moti fs), which are postulated to he involved in coupling ATP hydrolysis wi th other biological processes, The uup gene product shares extensive h omology with the deduced sequences of two proteins of Haemophilus infl uenzae., The uup gene is also situated immediately upstream of (and is transcribed in the same direction as) the paraquat-inducible SoxRS-re gulated pqi-5 gene, two reported promoters for which are situated with in the uup coding sequence.