The uvp1 gene on the R46 plasmid encodes a resolvase that catalyzes site-specific resolution involving the 5'-conserved segment of the adjacent integron In1.
The product of the uvp1 gene of the R46 plasmid, a member of the DNA invertase-resolvase family, was studied to characterize its recombination activity on the R46 plasmid. The purified Uvp1 protein specifically binds to a 256-bp DNA fragment located immediately upstream of the uvp1 gene itself, and overlapping the 5'-conserved segment (5'-CS) of the R46 integron In1. We identified on this fragment a putative resolution (res) site. Using an in vitro assay, we demonstrated the ability of the protein to resolve a synthetic cointegrate containing a direct repeat of the res site. In vivo, we obtained cointegrate resolution in Uvp1-expressing recA- cells. Sites I and II, subsites of the putative res site, lie within the outer boundary of the integron 5'-CS which is common to all the known integrons. Furthermore, a 69-bp DNA element (containing site I) is required for cointegrate resolution. We propose that this recombination mechanism protects R46 plasmid against unequal distribution following fusion with either identical or different integron-bearing plasmids. Moreover, Uvp1 might have a role in generating gene cassette diversity between the two conserved segments of the integron.
Tosini
F
F
Laboratorio di Biologia Cellulare, Reparto di Genetica Molecolare, Istituto Superiore di Sanità, Rome, Italy. tosini@vm.iss.it
Venanzi
S
S
Boschi
A
A
Battaglia
P A
PA
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D019426:Integrases / Q000378:metabolism*; D008969:Molecular Sequence Data; D010957:Plasmids; D045522:Recombinases; D015183:Restriction Mapping; D019895:Transposases / Q000378:metabolism*; D045564:Transposon Resolvases
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D045522:Recombinases; C061196:uvp1 protein, E coli; D019426:Integrases; D019895:Transposases; D045564:Transposon Resolvases