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Gene regulation by transmembrane signaling.
Volkmar Braun1, Susanne Mahren, Annette Sauter
1Microbiology/Membrane Physiology, University of Tübingen, Auf der Morgenstelle 28, Tübingen, 72096, Germany. volkmar.braun@mikrobio.uni-tuebingen.de
Summary
Ferric citrate transport in E. coli is regulated by a novel signaling pathway. External ferric citrate triggers a cascade across cell membranes, activating gene transcription without entering the cell.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Escherichia coli K-12 utilizes ferric citrate for iron uptake.
- Transcriptional regulation of ferric citrate transport genes is complex.
Purpose of the Study:
- To elucidate the novel mechanism of ferric citrate transport gene regulation in E. coli.
- To identify the key proteins and signaling pathways involved.
Main Methods:
- Investigated the roles of FecA, FecR, and FecI proteins.
- Studied the effect of ferric citrate on gene transcription.
- Examined the influence of iron availability and Fur repressor.
Main Results:
- Ferric citrate binding to outer membrane protein FecA initiates a signaling cascade.
- This cascade transmits signals across three cellular compartments: outer membrane, periplasm, and cytoplasmic membrane.
- FecR and FecI proteins mediate signal transduction to the cytoplasm, activating transcription of fecABCDE genes.
- Iron-dependent Fur repressor controls transcription of fecI and fecR genes.
Conclusions:
- Discovered a unique transmembrane signaling system for ferric citrate transport regulation.
- This system highlights a paradigm for gene regulation involving signaling across multiple cellular compartments.
- The regulation ensures efficient iron uptake under iron-limiting conditions.