Biological systems utilize light as the source of signal and energy, as seen in our vision and plants' photosynthesis, respectively. However, light is also harmful, because UV light damages DNA. Interestingly, biological system has an enzyme to repair the damaged DNA using light. Photochemical reactions of chromophore molecules in photoreceptive proteins initiate protein structural changes for various functions, whose mechanisms are of our particular interest. Light-induced difference Fourier-transform infrared (FTIR) spectroscopy is a powerful, sensitive and informative method to study structural changes of the chromophore, peptide backbone, side chains and protein-bound water molecules in photoreceptive proteins.Using light-induced difference FTIR spectroscopy, we have studied various rhodopsins, which function as visual and bacterial light sensors, light-driven ion pumps, or light-gated ion channels. Such multiple functions are initiated by common photochemistry, cis-trans isomerization of retinal. We also study flavin binding photoreceptors such as LOV domain, BLUF domain, and photolyase (PHR) and cryptochrome (CRY), whose photochemistry differs with each other, unlike rhodopsins. I will present the recent FTIR results of these photoreceptive proteins, possibly including the topics on (i) our color visual pigments, (ii) light-driven ion pumps, (iii) BLUF domain, and (iv) (6-4) PHR. Important role of water-containing hydrogen-bonding network will be discussed.

Light-induced difference FTIR spectroscopy of photoreceptive proteins

244th National Meeting (2012)

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