Mechanism
Light-gated ion channels function in a similar manner to other gated ion channels. When exposed to a certain stimulus, a conformational change occurs in the transmembrane proteins, which constitute the pore. This conformational change then opens or closes the ion channel, allowing for the flow of ions according to their electrochemical gradient. In the specific case of light-gated ion channels, the transmembrane proteins are usually coupled with a molecule that acts as a photoswitch. Retinal is a good example of a molecular photoswitch and is found in the naturally occurring Channelrhodopsins. The photoswitch absorbs a specific photon and changes its conformation, which, in turn, changes the conformation of the transmembrane proteins opening or closing the pore through which ions flow.
Read more about this topic: Light-gated Ion Channel
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