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. 1988 Jun;7(6):1881–1888. doi: 10.1002/j.1460-2075.1988.tb03021.x

Recognition of the P1 plasmid centromere analog involves binding of the ParB protein and is modified by a specific host factor.

M A Davis 1, S J Austin 1
PMCID: PMC457181  PMID: 3049080

Abstract

The P1 plasmid partition system is responsible for segregation of daughter plasmids during division of the Escherichia coli host cell. The P1-encoded elements consist of two essential proteins, ParA and ParB, and the cis-acting incB region. The incB region determines partition-mediated incompatibility and contains the centromere-like site parS. We have isolated and purified the two proteins. ParB binds specifically to the incB region in vitro. DNase I footprinting assays place a strong binding site over the 35-bp parS sequence previously shown to be sufficient for partition when the Par proteins are supplied in trans. A weaker site lies within the incB region in sequences that are important for specifying incompatibility, but are not essential for partition. Gel band retardation assays show that a host factor binds specifically to the incB sequence. The factor strongly stimulates binding of ParB. Cutting the region at a site between the two ParB binding sites yields two fragments that can bind ParB but not host factor. Thus, information for host-factor binding lies in the region determining the specificity of plasmid incompatibility. The roles of parB and the host factor in partition and the specificity of plasmid incompatibility are discussed.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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