ParB deficiency in Pseudomonas aeruginosa destabilizes the partner protein ParA and affects a variety of physiological parameters

Deletions leading to complete or partial removal of ParB were introduced into the Pseudomonas aeruginosa chromosome. Fluorescence microscopy of fixed cells showed that ParB mutants lacking the C-terminal domain or HTH motif formed multiple, less intense foci scattered irregularly, in contrast to the one to four ParB foci per cell symmetrically distributed in wild-type P. aeruginosa. All parB mutations affected both bacterial growth and swarming and swimming motilities, and increased the production of anucleate cells. Similar effects were observed after inactivation of parA of P. aeruginosa. As complete loss of ParA destabilized its partner ParB it was unclear deficiency of which protein is responsible for the mutant phenotypes. Analysis of four parB mutants showed that complete loss of ParB destabilized ParA whereas three mutants that retained the N-terminal 90 aa of ParB did not. As all four parB mutants demonstrate the same defects it can be concluded that either ParB, or ParA and ParB in combination, plays an important role in nucleoid distribution, growth and motility in P. aeruginosa

Vaccination de l'enfant voyageur en zone tropicale (vaccins d'aujourd'hui et perspectives)

TOULOUSE3-BU Santé-Centrale (315552105) / SudocSudocFranceF

Insight into centromere-binding properties of ParB proteins: a secondary binding motif is essential for bacterial genome maintenance

ParB proteins are one of the three essential components of partition systems that actively segregate bacterial chromosomes and plasmids. In binding to centromere sequences, ParB assembles as nucleoprotein structures called partition complexes. These assemblies are the substrates for the partitioning process that ensures DNA molecules are segregated to both sides of the cell. We recently identified the sopC centromere nucleotides required for binding to the ParB homologue of plasmid F, SopB. This analysis also suggested a role in sopC binding for an arginine residue, R219, located outside the helix-turn-helix (HTH) DNA-binding motif previously shown to be the only determinant for sopC-specific binding. Here, we demonstrated that the R219 residue is critical for SopB binding to sopC during partition. Mutating R219 to alanine or lysine abolished partition by preventing partition complex assembly. Thus, specificity of SopB binding relies on two distinct motifs, an HTH and an arginine residue, which define a split DNA-binding domain larger than previously thought. Bioinformatic analysis over a broad range of chromosomal ParBs generalized our findings with the identification of a non-HTH positively charged residue essential for partition and centromere binding, present in a newly identified highly conserved motif. We propose that ParB proteins possess two DNA-binding motifs that form an extended centromere-binding domain, providing high specificity