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Journal of Bacteriology, November 2001, p. 6234-6243, Vol. 183, No. 21
Warsaw University, Institute of Microbiology,
Department of Bacterial Genetics, 02-096 Warsaw, Poland
Received 11 June 2001/Accepted 6 August 2001
The replicator region of composite plasmid pTAV1 of
Paracoccus versutus (included in mini-replicon pTAV320)
belongs to the family of repABC replicons commonly found
in plasmids harbored by Agrobacterium and
Rhizobium spp. The repABC replicons
encode three genes clustered in an operon, which are involved in
partitioning (repA and repB) and
replication (repC). In order to localize the partitioning site of pTAV320, the two identified incompatibility determinants of this mini-replicon (inc1, located in the
intergenic sequence between repB and
repC; and inc2, situated downstream of
the repC gene) were PCR amplified and used together with
purified RepB fusion protein (homologous to the type B partitioning
proteins binding to the partitioning sites) in an electrophoretic
mobility shift assay. The protein bound only inc2,
forming two complexes in a protein concentration-dependent manner. The
inc2 region contains two long (14-bp) repeated sequences
(R1 and R2). Disruption of these sequences completely eliminates RepB
binding ability. R1 and R2 have sequence similarities with analogous
repeats of another repABC replicon of plasmid pPAN1 of
Paracoccus pantotrophus DSM 82.5 and with centromeric
sequences of the Bacillus subtilis chromosome. Excess
RepB protein resulted in destabilization of the
inc2-containing plasmid in Escherichia
coli. On the other hand, the inc2 region could
stabilize another unstable replicon in P. versutus when RepA and RepB were delivered in trans, proving that this
region has centromere-like activity. Thus, it was demonstrated that
repA, repB, and inc2
constitute a functional system for active partitioning of pTAV320.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.21.6234-6243.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Identification of the Partitioning Site within the
repABC-Type Replicon of the Composite Paracoccus
versutus Plasmid pTAV1
*
Corresponding author. Mailing address: Warsaw
University, Institute of Microbiology, Department of Bacterial
Genetics, Miecznikowa 1, 02-096 Warsaw, Poland. Phone: 48 22 5541402. Fax: 48 22 5541404. E-mail: bartosik{at}biol.uw.edu.pl.
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