Control of the Ferric Citrate Transport System of Escherichia coli : Mutations in Region 2.1 of the FecI Extracytoplasmic-Function Sigma Factor Suppress Mutations in the FecR Transmembrane Regulatory Protein
| Autor: | Martina Ochs, Alfred Stiefel, Petra T. Schindler, Volkmar Braun, Sabine Enz, Susanne Mahren |
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| Rok vydání: | 2001 |
| Předmět: |
Transcriptional Activation
Transcription Genetic Molecular Sequence Data Repressor Genetics and Molecular Biology Sigma Factor Ferric Compounds Microbiology chemistry.chemical_compound Bacterial Proteins Transcription (biology) Sigma factor RNA polymerase Escherichia coli Amino Acid Sequence Promoter Regions Genetic Molecular Biology Base Sequence biology Membrane transport protein Escherichia coli Proteins Membrane Transport Proteins Biological Transport Promoter Gene Expression Regulation Bacterial Molecular biology Transmembrane protein Repressor Proteins chemistry Mutation biology.protein Bacterial outer membrane Sequence Alignment Bacterial Outer Membrane Proteins |
| Zdroj: | Journal of Bacteriology. 183:162-170 |
| ISSN: | 1098-5530 0021-9193 |
| Popis: | Transcription of the ferric citrate transport genes is initiated by binding of ferric citrate to the FecA protein in the outer membrane of Escherichia coli K-12. Bound ferric citrate does not have to be transported but initiates a signal that is transmitted by FecA across the outer membrane and by FecR across the cytoplasmic membrane into the cytoplasm, where the FecI extracytoplasmic-function (ECF) sigma factor becomes active. In this study, we isolated transcription initiation-negative missense mutants in the cytoplasmic region of FecR that were located at four sites, L13Q, W19R, W39R, and W50R, which are highly conserved in FecR-like open reading frames of the Pseudomonas aeruginosa , Pseudomonas putida , Bordetella pertussis , Bordetella bronchiseptica , and Caulobacter crescentus genomes. The cytoplasmic portion of the FecR mutant proteins, FecR 1–85 , did not interact with wild-type FecI, in contrast to wild-type FecR 1–85 , which induced FecI-mediated fecB transport gene transcription. Two missense mutations in region 2.1 of FecI, S15A and H20E, partially restored induction of ferric citrate transport gene induction of the fecR mutants by ferric citrate. Region 2.1 of ς 70 is thought to bind RNA polymerase core enzyme; the residual activity of mutated FecI in the absence of FecR, however, was not higher than that of wild-type FecI. In addition, missense mutations in the fecI promoter region resulted in a twofold increased transcription in fecR wild-type cells and a partial restoration of fec transport gene transcription in the fecR mutants. The mutations reduced binding of the Fe 2+ Fur repressor and as a consequence enhanced fecI transcription. The data reveal properties of the FecI ECF factor distinct from those of ς 70 and further support the novel transcription initiation model in which the cytoplasmic portion of FecR is important for FecI activity. |
| Databáze: | OpenAIRE |
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