Absorption of light by the covalently-bound retinal chromophore of channelrhodopsin triggers a reaction cycle that involves proton transfer reactions and protein conformational changes. A key open question is how internal waters participate in the long-distance proton transfers. We addressed this question by performing systematic simulations of channelrhodopsin with different protonation states. We find that protein titratable groups connect to extensive water networks whose structure and dynamics is protonation-dependent. To identify structural elements that may function as gates, we carried out bioinformatics analyses [1,2] and simulations of a proton-pumping microbial rhodopsin, bacteriorhodopsin, mutated so as to mimic specific interactions of channelrhodopsin [2]. This led to the identification of an aspartate/threonine inter-helical motif that participates in controlling the local water and protein conformational dynamics.This work has been supported by the Marie Curie International Reintegration Award FP7-PEOPLE-2010-RG 276920 and by Project C4 of the DFG Collaborative Research Center SFB 1078 'Protonation Dynamics in Protein Function'.[1] Coral del Val, Jose Royuela-Flor, Stefan Milenkovic, Ana-Nicoleta Bondar (2013). Channelrhodopsins: a bioinformatics perspective. Biochimica et Biophysica Acta � Bioenergetics, Accepted, http://dx.doi.org/10.1016/j.bbabio.2013.11.005.[2] Coral del Val, Luiza Bondar, Ana-Nicoleta Bondar (2014). Coupling between inter-helical hydrogen bonding and water dynamics in a proton transporter. Journal of Structural Biology, Accepted, http://dx.doi.org/10.1016/j.jsb.2014.02.010.

Dynamics of the channelrhodopsin light-gated cation channel

248th National Meeting (2014)

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