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Journal of Bacteriology, May 1999, p. 2807-2815, Vol. 181, No. 9
School of Biological Sciences, University of
Birmingham, Edgbaston, Birmingham B15 2TT, United
Kingdom,1 and Department of Microbial
Biochemistry, Institute of Biochemistry and Biophysics, Warsaw,
Poland2
Received 3 August 1998/Accepted 24 February 1999
The korAB operon of broad-host-range plasmid RK2
encodes five genes, two of which, incC and
korB, belong to the parA and parB families, respectively, of genome partitioning functions. Both korB and a third gene, korA, are responsible
for coordinate regulation of operons encoding replication, transfer,
and stable inheritance functions. Overexpression of incC
alone caused rapid displacement of RK2. Using two different reporter
systems, we show that incC modulates the action of KorB.
Using promoter fusions to the reporter gene xylE, we show
that incC potentiates the repression of transcription by
korB. This modulation of korB activity was only
observed with incC1, which encodes the full-length IncC
(364 amino acids [aa]), whereas no effect was observed with
incC2, which encodes a polypeptide of 259 aa that lacks the
N-terminal 105 aa. Using bacterial extracts with IncC1 and IncC2 or
IncC1 purified through the use of a His6 tail and
Ni-agarose chromatography, we showed that IncC1 potentiates the binding
of KorB to DNA at representative KorB operators. The ability of IncC to
stabilize KorB-DNA complexes suggests that these two proteins work
together in the global regulation of many operons on the IncP-1
genomes, as well in plasmid partitioning.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
IncC of Broad-Host-Range Plasmid RK2 Modulates KorB
Transcriptional Repressor Activity In Vivo and Operator Binding
In Vitro
and
*
Corresponding author. Mailing address: School of
Biological Sciences, University of Birmingham, Edgbaston, Birmingham
B15 2TT, United Kingdom. Phone: 44-121-414-5903. Fax: 44-121-414-5925. E-mail: c.m.thomas{at}bham.ac.uk.
Present address: Division of Life Sciences, School of Natural
Sciences, University of Hertfordshire, Hatfield Campus, Hatfield, Hertfordshire AL10 9AB, United Kingdom.
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