Abstract
Microbes generally find it difficult to seek shelter from the Sun and must be able to sense and adjust to varying illumination conditions to protect themselves from light-induced damage. Sensory rhodopsins are a subset of the large family of archaeal and eubacterial rhodopsins. Unlike their ion-pumping brethren, they use an integral chromophore, a retinal derivative, to sense the wavelength of incident light and communicate this information through protein-protein interactions. Vogeley et al. describe the crystal structure of a cyanobacterial ( Anabaena ) sensory rhodopsin that has the unusual property of existing in two photoactive stable states; most rhodopsins are stable in a dark-adapted state and cycle through a sequence of conformational changes upon illumination. These orange- and blue-sensitive states would enable Anabaena to assess the quality (color composition) of ambient light and to adjust its repertoire of light-harvesting complexes. L. Vogeley, O. A. Sineshchekov, V. D. Trivedi, J. Sasaki, J. L. Spudich, H. Luecke, Anabaena sensory rhodopsin: A photochromic color sensor at 2.0 Å. Science 306 , 1390-1393 (2004). [Abstract] [Full Text]
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