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Barbara E Funnell

Publications and source records attributed to Barbara E Funnell.

4 recordsLinked to original sources
PubMed2005

Structures of ParB bound to DNA reveal mechanism of partition complex formation.

The faithful inheritance of genetic information, which is essential for all organisms, requires accurate DNA partition (segregation) at cell division. In prokaryotes, partition is mediated by par systems, for which the P1 plasmid system of Escherichia coli is a prototype comprising a partition site and two proteins, ParA and ParB. To form the partition complex necessary for segregation, P1 ParB must recognize a complicated arrangement of A-box and B-box DNA motifs located on opposite ends of a sharply bent parS partition site of approximately 74 bp (refs 3-7). Here we describe structures of ParB bound to partition sites. ParB forms an asymmetric dimer with extended amino-terminal HTH (helix-turn-helix) domains that contact A-boxes. The two HTH domains emanate from a dimerized DNA-binding module composed of a six-stranded beta-sheet coiled-coil that binds B-boxes. Strikingly, these individual DNA-binding modules rotate freely about a flexible linker, enabling them to contact several arrangements of A- and B-boxes. Most notably, each DNA-binding element binds to and thus bridges adjacent DNA duplexes. These unique structural features of ParB explain how this protein can bind complex arrays of A- and B-box elements on adjacent DNA arms of the looped partition site.

Base Sequence↗
PubMed2005

Partition-mediated plasmid pairing.

Plasmid partition systems are essential for the stability and thus the survival of low-copy-number plasmids in growing bacterial populations. The partition reaction is responsible for proper intracellular distribution of plasmids in the bacterial cell cycle. One common step in most partition models is the pairing of plasmids to each other by partition components. Here, evidence that supports the pairing of plasmids via their partition complexes is reviewed, and discussed in light of recent observations that many plasmids, including those without active partition systems are clustered in limited groups inside bacterial cells.

Bacterial Proteins↗
PubMed2005

Identification and characterization of a novel allele of Escherichia coli dnaB helicase that compromises the stability of plasmid P1.

Bacteriophage P1 lysogenizes Escherichia coli cells as a plasmid with approximately the same copy number as the copy number of the host chromosome. Faithful inheritance of the plasmids relies upon proper DNA replication, as well as a partition system that actively segregates plasmids to new daughter cells. We genetically screened for E. coli chromosomal mutations that influenced P1 stability and identified a novel temperature-sensitive allele of the dnaB helicase gene (dnaB277) that replaces serine 277 with a leucine residue (DnaB S277L). This allele conferred a severe temperature-sensitive phenotype to the host; dnaB277 cells were not viable at temperatures above 34 degrees C. Shifting dnaB277 cells to 42 degrees C resulted in an immediate reduction in the rate of DNA synthesis and extensive cell filamentation. The dnaB277 allele destabilized P1 plasmids but had no significant influence on the stability of the F low-copy-number plasmid. This observation suggests that there is a specific requirement for DnaB in P1 plasmid maintenance in addition to the general requirement for DnaB as the replicative helicase during elongation.

Adenosine Triphosphatases↗