title: Oligomerization and DNA binding of Ler, a master regulator of pathogenicity of enterohemorrhagic and enteropathogenic Escherichia coli.
abstract: Ler is a DNA-binding, oligomerizable protein that regulates pathogenicity islands in enterohemorrhagic and enteropathogenic Escherichia coli strains. Ler counteracts the transcriptional silencing effect of H-NS, another oligomerizable nucleoid-associated protein. We studied the oligomerization of Ler in the absence and presence of DNA by atomic force microscopy. Ler forms compact particles with a multimodal size distribution corresponding to multiples of 3-5 units of Ler. DNA wraps around Ler particles that contain more than 15-16 Ler monomers. The resulting shortening of the DNA contour length is in agreement with previous measurements of the length of DNA protected by Ler in footprinting assays. We propose that the repetition unit corresponds to the number of monomers per turn of a tight helical Ler oligomer. While the repressor (H-NS) and anti-repressor (Ler) have similar DNA-binding domains, their oligomerization domains are unrelated. We suggest that the different oligomerization behavior of the two proteins explains the opposite results of their interaction with the same or proximal regions of DNA.
authors.affiliation: Structural and Computational Biology, Institute for Research in Biomedicine, Department of Microbiology, University of Barcelona, Barcelona 08028, Spain. jesus.garcia@irbbarcelona.org
authors.forename: Jesús
authors.initials: J
authors.lastname: García
authors.forename: Tiago N
authors.initials: TN
authors.lastname: Cordeiro
authors.forename: María J
authors.initials: MJ
authors.lastname: Prieto
authors.forename: Miquel
authors.initials: M
authors.lastname: Pons
mesh_terms: D004269:DNA, Bacterial / Q000737:chemistry / Q000648:ultrastructure*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000648:ultrastructure; D054324:Enterohemorrhagic Escherichia coli / Q000235:genetics / Q000472:pathogenicity; D054308:Enteropathogenic Escherichia coli / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000648:ultrastructure; D018625:Microscopy, Atomic Force; D055503:Protein Multimerization; D015534:Trans-Activators / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C465556:Ler protein, E coli; D015534:Trans-Activators