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Localization and environmental regulation of MCP-like proteins in Rhodobacter sphaeroides
D M Harrison1, J Skidmore, J P Armitage
1Department of Biochemistry, University of Oxford, UK.
Molecular Microbiology
|February 27, 1999
Summary
Rhodobacter sphaeroides uses MCP-like chemoreceptors, regulated by environmental factors like light and redox state. These receptors localize to cell poles and cytoplasm, with expression varying based on growth conditions.
Area of Science:
- Microbiology
- Bacterial Chemotaxis
- Signal Transduction
Background:
- Chemotaxis in Rhodobacter sphaeroides involves chemoeffector transport and metabolism.
- Previous studies in phototrophically grown R. sphaeroides failed to identify MCP chemoreceptors homologous to those in E. coli.
- MCP-like proteins have been identified in R. sphaeroides WS8N using antibodies against conserved domains of E. coli Tsr.
Purpose of the Study:
- To identify and characterize MCP-like chemoreceptors in Rhodobacter sphaeroides.
- To investigate the environmental regulation and cellular localization of these MCP-like proteins.
- To explore the implications for chemosensory signaling and receptor oligomerization in R. sphaeroides.
Main Methods:
- Western blotting using antibodies against conserved domains of E. coli Tsr.
- Immunogold electron microscopy for cellular localization.
- Comparative analysis of receptor expression and distribution under different growth conditions (aerobic, anaerobic, light/dark).
Main Results:
- MCP-like proteins were identified in R. sphaeroides WS8N.
- Receptor expression is environmentally regulated, decreasing significantly (17-fold) in the light.
- Receptors localize to both cell poles and the cytoplasm, with altered distribution under different light and redox conditions.
Conclusions:
- MCP-like chemoreceptor expression in R. sphaeroides is controlled by redox state and light intensity.
- Receptor localization varies with environmental conditions, suggesting adaptation of the chemotaxis system.
- Cytoplasmic receptors can oligomerize, potentially explaining multiple chemosensory protein copies in R. sphaeroides.
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