The Channelrhodopsin Mechanism

Channelrhodopsins are light-gated ion channels that mediate vision in phototactic green algae and are used in the neurosciences to light-trigger action potentials in transfected cells, tissues and living animals (optogenetics). In the next three years we will further characterize Channelrhodopsins from Chlamydomonas, Volvox and Dunaliella in oocytes and HEK cells. We will further study and discriminate the two conducting states, we will more carefully analyze the proton dynamics of amino acid of the retinal binding pocket, the functional meaning of the complex Schiff-base counter ion, chromophore deprotonation for the gating mechanism, and the bridging between water filled ion channel and the catalytic chromophore cycle. We will establish in our laboratory as an neuronal test system electrical measurements on ChR-expressing hippocampal cells. We expect that the planned experiments will reveal the basic mechanism of light-gated ion channels and simultaneously provide new ChR-variants for application in the neurosciences.