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.
Original language | English |
---|---|
Pages (from-to) | 5665-72 |
Number of pages | 8 |
Journal | Journal of Bacteriology |
Volume | 176 |
Issue number | 18 |
Publication status | Published - Sep 1994 |
Keywords
- Bacterial Proteins/genetics
- Bacterial Proteins/metabolism
- Bacterial Proteins/physiology
- Base Sequence
- Binding Sites
- DNA, Bacterial/metabolism
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- DNA-Binding Proteins/physiology
- Escherichia coli/genetics
- Escherichia coli/physiology
- Escherichia coli Proteins
- Fimbriae Proteins
- Fimbriae, Bacterial/physiology
- Gene Expression Regulation, Bacterial/physiology
- Integrases
- Leucine-Responsive Regulatory Protein
- Molecular Sequence Data
- Mutation/physiology
- Recombination, Genetic
- Transcription Factors
- Transcription, Genetic/physiology