摘要： Rhodopsins are an ancient class of light-sensing membrane proteins that bind retinylidene chromophores in order to form pigments that absorb visible light. Light absorption triggers isomerization of the chromophore, which is bound covalently within the transmembrane core of the protein, an event that drives protein conformational changes. Type-1 rhodopsins are also known as microbial rhodopsins, which include the well-known light-driven protein pump bacteriorhodopsin found in archeabacteria. Type-2 rhodopsins, or animal rhodopsins, include the sensory rhodopsins used as visual pigments found in most animals, including humans. Both Type-1 and -2 rhodopsins share a canonical seven-transmembrane helical polytopic structure with their amino terminal tails projecting to the topological outside of the cell membrane. Rhodopsins harness light energy to perform a vast array of functions, including pumping ions, gating channel activity, activating coupled enzyme systems, and transducing light sensation in vision. Pushkarev et al. have now reported the discovery of an entirely new group of microbial rhodopsins, opening up the potential for the elucidation of an extensive new class of rhodopsins that they term “heliorhodopsins.”