Eye rhodopsin is a protein that is very sensitive to light, located in our retina. This pigment comes into play for twilight and night vision. In archaea, bacteria, single cell eukaryots and even viruses there are genes related molecules called microbial rhodopsins, which plays a major role in the capture of solar energy. These molecules have found essential applications in medicine in the field of neuroscience, being at the heart of optogenetics - biotechnology for optical control of living cells, tissues and organs such as brain. It appeared that these light-driven proteins perform highly diverse functions, they are very abundant and are major light harvesting proteins in the sea. 

Yet the structure, function and biological role of the most of the rhodopsins are unknow. This does not allow one to fully use their great potential for biotechnological applications. 

Researchers from CEA-Irig (IBS) have recently published three papers on the structural biology and functional characterization of several new microbial rhodopsins. First, the researchers worked on the family of heliorhodopsins (ref1), demonstrating that these proteins are probably unique photoenzymes with unusual architecture and they may be involved in fundamental processes on the Earth such as the carbon cycle. Next, they determined the molecular mechanism of a light-controlled sodium pump by studying the structure of rhodopsin KR2 in its active state (ref2). This can be an important step towards engineering of long thought optogenetic tools. Finally, the scientists characterized two members of viral rhodopsins (ref3), and showed that they are photogenic Na+/K+ selective channels, inhibited by Ca2+. They resolved the structure of one of them at 1.4 Å and showed their potential for optogenetic applications. The authors hypothesized that viral rhodopsin channels may be involved in regulation of phytoplankton and in this way may influence climate and ecology.