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Max Planck Institute Magdeburg CNV-Meeting September 16 th 2011 Redox Sensors for Photosystem Regulation in Rhodospirillum rubrum Anke Carius MAX-PLANCK-INSTITUT.

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Presentation on theme: "Max Planck Institute Magdeburg CNV-Meeting September 16 th 2011 Redox Sensors for Photosystem Regulation in Rhodospirillum rubrum Anke Carius MAX-PLANCK-INSTITUT."— Presentation transcript:

1 Max Planck Institute Magdeburg CNV-Meeting September 16 th 2011 Redox Sensors for Photosystem Regulation in Rhodospirillum rubrum Anke Carius MAX-PLANCK-INSTITUT DYNAMIK KOMPLEXER TECHNISCHER SYSTEME MAGDEBURG Max Planck Institute for Dynamics of Complex Technical Systems Magdeburg/Germany

2 Max Planck Institute Magdeburg Structure Introduction: Rhodospirillum rubrum Theory of known redox regulators Experiments & Results Outlook

3 Max Planck Institute Magdeburg Introduction

4 Max Planck Institute Magdeburg Rhodospirillum rubrum Alpha-Proteobacterium Versatile metabolism Anoxygenic photosynthesis Aerobic, semiaerobic and anaerobic conditions

5 Max Planck Institute Magdeburg The facultative phototrophic R. rubrum anaerobicaerobicsemiaerobic Photosynthetic membrane (PM) expression is redox dependent Therewith it can be influenced by substrate and oxygen supply Reverse, PM reflect the culture redox potential PM can be easily detected at 880 nm in a photospectrometer - O 2 + O 2 PM repressed PM expressed

6 Max Planck Institute Magdeburg Use of purple bacteria in science and industry Redox regulation and homeostasis science Microaerobic metabolism Precursor of mitochondria Biotechnological production of bacteriochlorophylls and carotenoids Various other potentially useful features: CO-utilization, CO 2 -fixation, PHB-production, H 2

7 Max Planck Institute Magdeburg Theory of known redox regulators

8 Max Planck Institute Magdeburg Activator Proteins: Enhance mRNA-Synthesis higher gene expression Repressor-Proteins: Inhibit mRNA-Synthesis reduced gene expression Antirepressor Proteins: Remove repressor allow gene expression Genetic Regulators RNA-Pol. DNA RNA-Pol. DNA

9 Max Planck Institute Magdeburg Thiolgroups as Redox Sensors: Sensor and Regulator in one Protein SH Reducing conditions SH S-S S S-… S S S S S - O 2 + O 2 Oxidizing conditions

10 Max Planck Institute Magdeburg CrtJ/PpsR: An Example Thiol-based redox sensor Repressor function Photosensitive antirepressor R. rubrum posesses a PpsR-homologue Masuda et al. 2002, Repression of photosynthesis gene expression in Rhodobacter sphaeroides, Proc Natl Acad Sci USA, 10(99)

11 Max Planck Institute Magdeburg Bauer et al Signal Transduction By The Global Regulator RegB Is Mediated By A Redox Active Cysteine. EMBO J. 22, The Two Component System: RegB/RegA RegB: Redoxsensorkinase RegA: Response regulator, activator Quinone pool based redox signal Supposed to integrate cellular thiol redox potential Control of gene expression R. rubrum posesses no RegB/A-homologues … but a histidine kinase close to the photosynthetic gene cluster….

12 Max Planck Institute Magdeburg Experiments & Results

13 Max Planck Institute Magdeburg Chemical triggering of redoxsensors Idea: Use of reductants to reduce thiol-groups Triggering of redox switch Reducing Agents: Dithiothreitol (DTT), Glutathione (GSH) Oxidizing Agents: Diethylmaleate (DEM), ox. Glutathione (GSSG) DTT: Reduces all thiol groups of proteins GSH: Reduces some thiol group via specific interactions DEM: Lowers the amount of reduced GSH in the cell

14 Max Planck Institute Magdeburg Growth experiments

15 Max Planck Institute Magdeburg PpsR in R. rubrum Results hint on a specific regulation via GSH Measurements of cytosolic GSH: Active uptake of GSH ! PpsR as a thiol redox sensor was deleted Mutants were unable to produce PM! PpsR in R. rubrum must be an activator protein PpsR binds more DNA under reducing conditions

16 Max Planck Institute Magdeburg Outlook Deletion mutant of histidine kinase close to photosynthetic genes Identification of PpsR binding motive Complementation of PpsR-deletion mutant Overexpression of PpsR in R. rubrum

17 Max Planck Institute Magdeburg Thank you very much for your attention!


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