The joint research article "A protonation-coupled feedback mechanism controls the signalling process in bathy phytochromes" by the SFB members Francisco Velazquez Escobar and Patrick Piwowarski from the research projects of Prof. Peter Hildebrandt (project B6) and Prof. Franz Bartl (project B5) in cooperation with Prof. Maria Andrea Mroginski (project C3) as well as Dr. Bilal Qureshi and Dr. Patrick Scheerer (both project B6) is now published online by Nature Chemistry (1). The article can be accessed ahead of print on the website of the high-impact journal from the Nature Publishing Group.

The presented research is a result of intensive collaborations across disciplinary borders within the SFB 1078 investigating protonation dynamics in protein function. In their article, Velazquez Escobar and Piwowarski et al. describe a mechanistic pattern, which involves proton translocation within the protein, providing novel insight into the molecular functioning of phytochromes.

Phytochromes are photoreceptors composed of a photosensor including a chromophore group and a regulatory output module. They function as bimodal photoswitches, in which the photosensor is interconverted between two states to activate and deactivate the attached output module.

Using resonance Raman and infrared difference spectroscopy, the SFB researchers are able to monitor the functional groups that take part in the proton-coupled structural changes. Their study reveals that proton translocation in the chromophore pocket of the photosensor couple chromophore and protein structural changes in a way that leads to the formation of the photoactivated state and thus (de)activation of the output model. Concomitantly, the proton re-arrangements open the pathway for the reversal of this process, corresponding to a negative feedback mechanism.

The published results are constituent to the doctoral research of Francisco Velazquez Escobar, who recently defended his thesis successfully. Congratulations!!!

Reference:

1. Velazquez Escobar, F., Piwowarski, P., Salewski, J., Michael, N., Fernandez Lopez, M., Rupp, A., Muhammad Qureshi, B., Scheerer, P., Bartl, F., Frankenberg-Dinkel, N., Siebert, F., Mroginski, M.A., and Hildebrandt P. (2015). A protonation-coupled feedback mechanism controls the signalling process in bathy phytochromes. Nature Chemistry 7, 423-430. (doi: 10.1038/nchem.2225).