Berlin 2012 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 7: Posters: Proteins
BP 7.42: Poster
Montag, 26. März 2012, 17:30–19:30, Poster A
Modeling the Light-Dependent Repression of Photosynthesis Genes by the AppA/PpsR System in Rhodobacter sphaeroides — •Rakesh Pandey1, Dietrich Flockerzi1, Marcus J. B. Hauser2, and Ronny Straube1 — 1Max Planck Institute for Dynamics of Complex Technical Systems, Magdeburg — 2Institute of Experimental Physics, Otto-von-Guericke University, Magdeburg
Purple bacteria derive energy from aerobic respiration or photosynthesis (PS) depending on the availability of oxygen and light. Under aerobic conditions, PS genes are specifically repressed by the PpsR protein. In R. sphaeroides, the repressive action of PpsR is antagonized by the blue-light sensitive flavoprotein AppA which forms transcriptionally inactive complexes with PpsR under anaerobic conditions. However, under semi-aerobic conditions blue-light excitation of AppA causes the AppA-PpsR complexes to dissociate leading, again, to PS gene repression. We have recently proposed a simple mathematical model [1] which suggests that this phenotype arises from the formation of a maximum in the response curve of PpsR at intermediate oxygen levels. Here, we present an extended model which incorporates a more realistic mechanism for the light regulation. Its predictions compare favorably with experimental results on the light-dependent repression of PS genes under semi-aerobic conditions. We also identify potential kinetic and stoichiometric constraints that the interplay between light and redox regulation imposes on the functionality of the AppA/PpsR system, especially with respect to a possible bistable response. [1] Pandey R, Flockerzi D, Hauser MJB, Straube R. Biophys. J. 100, 2347 (2011).