title: Leucine-responsive regulatory protein Lrp and PapI homologues influence phase variation of CS31A fimbriae.
abstract: CS31A, a K88-related surface antigen specified by the clp operon, is a member of the type P family of adhesive factors and plays a key role in the establishment of disease caused by septicemic and enterotoxigenic Escherichia coli strains. Its expression is under the control of methylation-dependent transcriptional regulation, for which the leucine-responsive regulatory protein (Lrp) is essential. CS31A is preferentially in the OFF state and exhibits distinct regulatory features compared to the regulation of other P family members. In the present study, surface plasmon resonance and DNase I protection assays showed that Lrp binds to the distal moiety of the clp regulatory region with low micromolar affinity compared to its binding to the proximal moiety, which exhibits stronger, nanomolar affinity. The complex formation was also influenced by the addition of PapI or FooI, which increased the affinity of Lrp for the clp distal and proximal regions and was required to induce phase variation. The influence of PapI or FooI, however, was predominantly associated with a more complete shutdown of clp expression, in contrast to what has previously been observed with AfaF (a PapI ortholog). Taken together, these results suggest that the preferential OFF state observed in CS31A cells is mainly due to the weak interaction of the leucine-responsive regulatory protein with the clp distal region and that the PapI homolog favors the OFF phase. Within the large repertoire of fimbrial variants in the P family, our study illustrates that having a fimbrial operon that lacks its own PapI ortholog allows it to be more flexibly regulated by other orthologs in the cell.
authors.affiliation: Groupe de Recherche sur les Maladies Infectieuses du Porc (GREMIP) and Centre de Recherche en Infectiologie Porcine (CRIP), Université de Montréal, Saint-Hyacinthe, Quebec, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Graveline
authors.affiliation: Groupe de Recherche sur les Maladies Infectieuses du Porc (GREMIP) and Centre de Recherche en Infectiologie Porcine (CRIP), Université de Montréal, Saint-Hyacinthe, Quebec, Canada.
authors.forename: Philippe
authors.initials: P
authors.lastname: Garneau
authors.affiliation: Institut National de la Recherche Agronomique, Saint-Genès-Champanelle, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Martin
authors.affiliation: Groupe de Recherche sur les Maladies Infectieuses du Porc (GREMIP) and Centre de Recherche en Infectiologie Porcine (CRIP), Université de Montréal, Saint-Hyacinthe, Quebec, Canada.
authors.forename: Michaël
authors.initials: M
authors.lastname: Mourez
authors.affiliation: McGill University Surface Plasmon Resonance (SPR) Facility, Montréal, Quebec, Canada.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Hancock
authors.affiliation: Groupe de Recherche sur les Maladies Infectieuses du Porc (GREMIP) and Centre de Recherche en Infectiologie Porcine (CRIP), Université de Montréal, Saint-Hyacinthe, Quebec, Canada.
authors.forename: Rémi
authors.initials: R
authors.lastname: Lavoie
authors.affiliation: Groupe de Recherche sur les Maladies Infectieuses du Porc (GREMIP) and Centre de Recherche en Infectiologie Porcine (CRIP), Université de Montréal, Saint-Hyacinthe, Quebec, Canada josee.harel@umontreal.ca.
authors.forename: Josée
authors.initials: J
authors.lastname: Harel
mesh_terms: D000942:Antigens, Bacterial / Q000096:biosynthesis*; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D051756:Leucine-Responsive Regulatory Protein / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism*; D020349:Surface Plasmon Resonance
chemical_list: D000942:Antigens, Bacterial; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C497278:Lrp protein, E coli; C086707:PapI protein, E coli; D012097:Repressor Proteins; D051756:Leucine-Responsive Regulatory Protein; C071730:clpG protein, E coli