Disease relevance of parB

• The partition system of P1 plasmids is composed of two proteins, ParA and ParB, and a cis-acting site parS. parS is wrapped around ParB and Escherichia coli IHF protein in a higher order nucleoprotein complex called the partition complex [1].
• Stable maintenance of the plasmid prophage of bacteriophage P1 requires the P1 ParB protein, which acts on a DNA site termed parS [2].
• In Caulobacter crescentus the partitioning proteins ParA and ParB operate a molecular switch that couples chromosome partitioning to cytokinesis [3].
• The partition system of the low-copy-number plasmid/prophage of bacteriophage P1 encodes two proteins, ParA and ParB, and contains a DNA site called parS [4].

High impact information on parB

• The partition module of plasmid P1 is typical and consists of a centromere site, parS, and genes that encode proteins ParA and ParB [5].
• The ParA protein contacts the par operon operator for operon autoregulation, and the ParB contacts the parS partition site during partition [6].
• We found that ParB participates in autoregulation at the operator site by making a specific contact with ParA [6].
• They include a second ParB binding site and a site for the host integration host factor protein [7].
• Finally, inhibition of cell division did not inhibit localization of ParB foci in cells, indicating that the positioning signals in the E. coli host that are needed for P1 partition do not depend on early division events [8].

Biological context of parB

• A 34 bp segment is essential for partition and binds the plasmid ParB protein [7].
• The visualization of ParB foci depended completely on the presence of parS, although their visualization was independent of the chromosomal context of parS (in P1 or the bacterial chromosome) [8].
• The P1 plasmid partition complex at parS. II. Analysis of ParB protein binding activity and specificity [9].
• Productive interaction between the chromosome partitioning proteins, ParA and ParB, is required for the progression of the cell cycle in Caulobacter crescentus [3].
• Through in vitro binding experiments, purified ParB was shown to interact specifically with the par promoter region [10].

Anatomical context of parB

• ParA may facilitate ParB movement along the inner surface of the cytoplasmic membrane to encounter and become tethered to the next replication zone [11].

Associations of parB with chemical compounds

• The motifs containing the specificity dinucleotides and the primary ParB binding (heptamer) sites bear no obvious relationship of spacing or orientation to each other [12].
• Using mixtures of ParB and a larger polyhistidine-tagged version of ParB (His-ParB) in DNA binding assays, we determined that the initial I + B1 complex contains one dimer of ParB [13].
• Purified glutathione S-transferase-InvE fusion protein bound directly to the -93 to -54 region (designating the icsB transcription start site as nucleotide +1) containing the ParB BoxA-like sequence [14].

Analytical, diagnostic and therapeutic context of parB

• By immunofluorescence microscopy, we observed that ParB localizes to discrete foci that are most often located close to the one-quarter and three-quarters positions of cell length [8].
• Shift Western blotting experiments indicated that the I + B2 complex contained twice as much ParB as the I + B1 complex [13].
• Measured by gel mobility shift assays, ParB and IHF bind tightly to parS and form a specific complex, called I + B1 [13].
• Recombinant ParA and ParB proteins were overexpressed and purified by affinity chromatography [10].

References