Microbial rhodopsins constitute a large and diverse superfamily of light-driven membrane proteins. They perform ion transport and signal transduction across cell membranes, but also work as photosensors and enzymes. Microbial rhodopsins play critical biological and ecological roles, allowing small organisms such as Archaea, Bacteria, simple Eukaryota, and even Viruses to utilize solar energy for their life. Rhodopsins also have invaluable practical importance. They are the core of optogenetics - the biotechnology to control living cells and tissues with light. Optogenetics revolutionized neuroscience and showed great potential for the treatment of Parkinson’s and Alzheimer’s diseases, recovery of the hearing, etc. Due to the development of functional metagenomics, more than 10,000 genes of rhodopsins were identified during the last decade. These include rhodopsins from giant viruses, light-driven sodium pumps, light-driven inward proton pumps, light-gated cation and anion channels, enzymorhodopsins, heliorhodopsins. Unfortunately, despite the great significance and importance of rhodopsin, only a few of them were investigated. In the seminar, I will describe our results on the structural and functional characterization of novel microbial rhodopsins, including light-driven sodium pump KR2, two rhodopsins from giant viruses, OLVPR1 and OLPVRII, and a member of a distinct family of heliorhodopsins, 48C12. High-resolution structures of these proteins in the ground and active states, together with spectroscopy and mutational analysis, allowed us to propose the mechanisms of their work as well as their biological roles.

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