title: Centromere binding specificity in assembly of the F plasmid partition complex.
abstract: The segregation of plasmid F of Escherichia coli is highly reliable. The Sop partition locus, responsible for this stable maintenance, is composed of two genes, sopA and sopB and a centromere, sopC, consisting of 12 direct repeats of 43 bp. Each repeat carries a 16-bp inverted repeat motif to which SopB binds to form a nucleoprotein assembly called the partition complex. A database search for sequences closely related to sopC revealed unexpected features that appeared highly conserved. We have investigated the requirements for specific SopB-sopC interactions using a surface plasmon resonance imaging technique. We show that (i) only 10 repeats interact specifically with SopB, (ii) no base outside the 16-bp sopC sites is involved in binding specificity, whereas five bases present in each arm are required for interactions, and (iii) the A-C central bases contribute to binding efficiency by conforming to a need for a purine-pyrimidine dinucleotide. We have refined the SopB-sopC binding pattern by electro-mobility shift assay and found that all 16 bp are necessary for optimal SopB binding. These data and the model we propose, define the basis of the high binding specificity of F partition complex assembly, without which, dispersal of SopB over DNA would result in defective segregation.
authors.affiliation: Université de Toulouse, INSA, UPS, INP, LISBP, Toulouse, France.
authors.forename: Flavien
authors.initials: F
authors.lastname: Pillet
authors.forename: Aurore
authors.initials: A
authors.lastname: Sanchez
authors.forename: David
authors.initials: D
authors.lastname: Lane
authors.forename: Véronique
authors.initials: V
authors.lastname: Anton Leberre
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Bouet
mesh_terms: D020029:Base Pairing; D001483:Base Sequence; D001665:Binding Sites; D002503:Centromere / Q000737:chemistry* / Q000378:metabolism; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D005144:F Factor / Q000235:genetics*; D055029:Inverted Repeat Sequences; D008956:Models, Chemical; D008969:Molecular Sequence Data; D011485:Protein Binding; D012091:Repetitive Sequences, Nucleic Acid; D020349:Surface Plasmon Resonance
chemical_list: D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C489223:SopB protein, E coli