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Discovery of a novel type of photo-receptive membrane protein,“Heliorhodopsin”

Nagoya Institute of Technology
The University of Tokyo
Japan Science and Technology Agency (JST)

Overview:

A research group discovered a novel type of photo-receptive membrane protein, rhodopsin, and it was named “Heliorhodopsin”. This research was achieved by the research group of Professor Hideki Kandori, Associate Professor Keiichi Inoue (Present at the Institute for Solid State Physics, the University of Tokyo), Research Associate Professor Satoshi P. Tsunoda at OptoBio Technology Research Center, Nagoya Institute of Technology, in collaboration with the group of Professor Oded Béjà at Technion Israel Institute of Technology, Israel.

The research revealed that the amino-acid sequence of this new rhodopsin is highly different from that of type-1 and type-2 rhodopsins which were derived from micro-organisms and animals, respectively. Despite of this large differences of the sequence, it was found that heliorhodopsin binds the same type of retinal molecule as type-1 rhodopsin, and shows similar photoreaction process involving retinal-isomerization and proton transfer reaction upon light illumination (Figure).

On the basis of this discovery of heliorhodopsin, the presence of a new photobiological strategy to use sun-light by the living organisms on the Earth was suggested.

The research paper was published in the Nature online (June 20, 2018).

Figure. The photo-reaction cycle of heliorhodopsin Heliorhodopsin shows photo-isomerization of retinal molecule and proton transfer reaction upon light illumination. Despite of large difference in amino-acid sequence, it shows a photo-reaction cycle involving K, M and O intermediate which is similar to that of type-1 rhodopsin. On the other hand, the detailed biophysical analysis revealed the distinct molecular aspects of heliorhodopsin different from type-1.
Figure. The photo-reaction cycle of heliorhodopsin
Heliorhodopsin shows photo-isomerization of retinal molecule and proton transfer reaction upon light illumination. Despite of large difference in amino-acid sequence, it shows a photo-reaction cycle involving K, M and O intermediate which is similar to that of type-1 rhodopsin. On the other hand, the detailed biophysical analysis revealed the distinct molecular aspects of heliorhodopsin different from type-1.

Reference:

(Published on: Thursday June 21st, 2018)