Modulation of the sensitivity of FimB recombination to branched-chain amino acids and alanine in Escherichia coli K-12.

Lahooti, Maryam and Roesch, Paula L. and Blomfield, Ian C. (2005) Modulation of the sensitivity of FimB recombination to branched-chain amino acids and alanine in Escherichia coli K-12. Journal of Bacteriology, 187 . pp. 6273-6280. (Access to this publication is restricted)

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Abstract

Phase variation of type 1 fimbriae of Escherichia coli requires the site-specific recombination of a short invertible element. Inversion is catalyzed by FimB (switching in either direction) or FimE (inversion mainly from on to off) and is influenced by auxiliary factors integration host factor (IHF) and leucine-responsive regulatory protein (Lrp). These proteins bind to sites (IHF site II and Lrp sites 1 and 2) within the invertible element to stimulate recombination, presumably by bending the DNA to enhance synapses. Interaction of Lrp with a third site (site 3) cooperatively with sites 1 and 2 (termed complex 1) impedes recombination. Inversion is stimulated by the branched-chain amino acids (particularly leucine) and alanine, and according to a current model, the amino acids promote the selective loss of Lrp from site 3 (complex 2). Here we show that the central portion of the fim invertible element, situated between Lrp site 3 and IHF site II, is dispensable for FimB recombination but that this region is also required for full amino acid stimulation of inversion. Further work reveals that the region is likely to contain multiple regulatory elements. Lrp site 3 is shown to bind the regulatory protein with low affinity, and a mutation that enhances binding to this element is found both to diminish the stimulatory effects of IVLA on FimB recombination and to inhibit recombination in the absence of the amino acids. The results obtained emphasize the importance of Lrp site 3 as a control element but also highlight the complexity of the regulatory system that affects this site.

Item Type: Article
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences > Biomedical Research Group
Depositing User: Sue Davies
Date Deposited: 19 Dec 2007 17:44
Last Modified: 12 May 2014 10:52
Resource URI: http://kar.kent.ac.uk/id/eprint/17 (The current URI for this page, for reference purposes)
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