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Modeling the Light- and Redox-Dependent Interaction of PpsR/AppA in Rhodobacter sphaeroides

MPG-Autoren
http://pubman.mpdl.mpg.de/cone/persons/resource/persons86208

Pandey,  R.
International Max Planck Research School (IMPRS);
Analysis and Redesign of Biological Networks, Max Planck Institute for Dynamics of Complex Technical Systems, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons86167

Flockerzi,  D.
Systems and Control Theory, Max Planck Institute for Dynamics of Complex Technical Systems, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons86233

Straube,  R.
Analysis and Redesign of Biological Networks, Max Planck Institute for Dynamics of Complex Technical Systems, Max Planck Society;

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Zitation

Pandey, R., Flockerzi, D., Hauser, M., & Straube, R. (2011). Modeling the Light- and Redox-Dependent Interaction of PpsR/AppA in Rhodobacter sphaeroides. Biophysical Journal, 100(10), 2347-2355. doi:10.1016/j.bpj.2011.04.017.


Zitierlink: http://hdl.handle.net/11858/00-001M-0000-0013-8D1C-3
Zusammenfassung
Facultative photosynthetic bacteria switch their energy generation mechanism from respiration to photosynthesis depending on oxygen tension and light. Part of this transition is mediated by the aerobic transcriptional repressor PpsR. In Rhodobacter sphaeroides, the repressive action of PpsR is antagonized by the redox- and blue-light-sensitive flavoprotein AppA which results in a unique phenotype: The repression of photosynthesis genes at intermediate oxygen levels and high light intensity, which is believed to reduce the risk of photooxidative stress. To analyze the underlying mechanism we developed a simple mathematical model based on the AppA-dependent reduction of a disulfide bond in PpsR and the light-sensitive complex formation between the reduced forms of AppA and PpsR. A steady-state analysis shows that high light repression can indeed occur at intermediate oxygen levels if PpsR is reduced on a faster timescale than AppA and if the electron transfer from AppA to PpsR is effectively irreversible. The model further predicts that if AppA copy numbers exceed those of PpsR by at least a factor of two, the transition from aerobic to anaerobic growth mode can occur via a bistable regime. We provide necessary conditions for the emergence of bistability and discuss possible experimental verifications. copyright 2011 by the Biophysical Society [accessed 2013 July 2nd]