title: The leucine-responsive regulatory protein binds to the fim switch to control phase variation of type 1 fimbrial expression in Escherichia coli K-12.
abstract: Phase variation of type 1 fimbriation in Escherichia coli is associated with the site-specific recombination of a 314-bp DNA invertible element. The fim switch directs transcription of fimA, the major fimbrial subunit gene, in one orientation (on) but not the other (off). Switching requires either fimB (on-to-off or off-to-on inversion) or fimE (on-to-off inversion only) and is reduced sharply in strains containing lrp::Tn10 mutations. Both fimE-promoted switching and fimB-promoted switching are stimulated by the amino acids alanine, isoleucine, leucine, and valine, and this regulation requires lrp. Here it is shown that the leucine-responsive regulatory protein (Lrp) binds in and adjacent to the fim switch. Mutations in fim that lower Lrp binding in vitro have corresponding effects on both fimB-promoted switching and fimE-promoted switching in vivo. Lrp initiates binding at one of two sites within the fim switch. Additional cooperative binding results in an extensive region of protection from both DNase I and 1,10-phenanthroline-copper complex-activated DNA cleavage. The region of protection can extend to within 12 bp of the right inverted repeat (switch off) and occupies over one-third of the switch. It is proposed that wrapping of fim DNA around an Lrp complex is required to form a recombination-proficient structure.
authors.affiliation: Department of Microbiology and Immunology, Bowman Gray School of Medicine, Winston-Salem, North Carolina 27157-1064.
authors.forename: D L
authors.initials: DL
authors.lastname: Gally
authors.forename: T J
authors.initials: TJ
authors.lastname: Rucker
authors.forename: I C
authors.initials: IC
authors.lastname: Blomfield
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D001483:Base Sequence; D001665:Binding Sites; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology; D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D019426:Integrases; D051756:Leucine-Responsive Regulatory Protein; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology; D011995:Recombination, Genetic; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C497278:Lrp protein, E coli; D014157:Transcription Factors; C081956:fimB protein, E coli; C081955:fimE protein, E coli; C063055:fimbrillin; D051756:Leucine-Responsive Regulatory Protein; D036781:Fimbriae Proteins; D019426:Integrases