Light-energy Conversion by Photoreceptive Proteins

Abstract

Photoreceptive proteins absorb light by chromophore molecule, and convert light into energy or signal. Ultrafast photoreactions such as electron transfer and isomerization allow efficient transitions from the electronically excited state of the chromophore, and stored light energy is utilized for each function. In case of light-energy conversion, light energy is finally stored as membrane potential, where proton is a principal component. Quinone pool facilitated by proton-coupled electron transfer in photosynthetic reaction center is a smart system to gain proton motive force. In contrast, light-driven ion pumping rhodopsins directly translocate protons, cations and anions. Ion-transporting rhodopsins are key tools in optogenetics, which revolutionize life sciences by control with light.