Abstract
Many organisms including human beings have rhodopsin as photoreceptor. In cell membranes of archaeal Halobacterium salinarum, there exist four rhodopsin-like proteins (so-called archaeal rhodopsins). Two of these work as light-driven ion pumps. The other two work as photosensors and are named sensory rhodopsin (sR) and phoborhodopsin (pR). pR mediates the negative phototaxis. Recently, X-ray crystallographic structure of pR derived from Natronobacterium pharaonis is reported, and allows us to investigate the function-structure relationship at atomic level. In this review, we describe our results on the photochemistry and the signal transduction mechanism of pR.
