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Redox signaling: globalization of gene expression
1Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center, Medical School, 6431 Fannin, Houston, TX 77030, USA.
The EMBO Journal
|August 16, 2000
Summary
Electron flow through the cbb(3) oxidase in Rhodobacter sphaeroides inversely regulates photosynthesis gene expression. This regulation involves intramolecular electron transfer and is modulated by the quinone pool and AppA-PpsR system.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Photosynthesis gene expression in Rhodobacter sphaeroides is regulated by environmental factors like oxygen and light.
- The cbb(3) oxidase and the PrrBA two-component system play crucial roles in this regulation.
- The AppA-PpsR antirepressor-repressor system also influences photosynthesis gene transcription via the quinone pool's redox state.
Purpose of the Study:
- To elucidate the regulatory mechanism of photosynthesis gene expression by the cbb(3) oxidase in Rhodobacter sphaeroides.
- To investigate the role of intramolecular electron transfer in signal generation by the cbb(3) oxidase.
- To understand how interacting regulatory circuits involving the cbb(3) oxidase, quinone pool, and AppA-PpsR system control gene expression.
Main Methods:
- Site-directed mutagenesis was employed to study the function of the cbb(3) oxidase.
- Analysis of electron flow through the cbb(3) oxidase.
- Investigation of gene expression levels, particularly for photosynthesis genes controlled by the PrrBA system.
- Characterization of the AppA-PpsR antirepressor-repressor system's interaction with the quinone pool.
Main Results:
- Electron flow through the cbb(3) oxidase is inversely proportional to the expression of PrrBA-controlled photosynthesis genes.
- Intramolecular electron transfer within the cbb(3) oxidase is essential for signal generation and transduction, independent of molecular oxygen.
- The redox state of the quinone pool, acting through the AppA-PpsR system, also modulates the transcription rate of the puc operon.
Conclusions:
- A model is proposed integrating the cbb(3) oxidase, quinone pool, and AppA-PpsR system to explain oxygen and light regulation of photosynthesis gene expression.
- The cbb(3) oxidase acts as a sensor, generating an inhibitory signal proportional to electron flow to repress photosynthesis gene expression.
- These findings reveal complex, interacting regulatory circuits governing photosynthesis in Rhodobacter sphaeroides.