Phototropins, blue-light receptors in plants, are light-activated serine/threonine kinases with a flavoprotein LOV domain as their light-sensing module. In addition to the phototropins found in eukaryotes, gene-sequence analysis predicts that LOV domains should be present in prokaryotes and archaea. Swartz et al. (see the Perspective by Kennis and Crosson) show that a subset of genes in prokaryotes encodes for proteins that function as light-activated LOV-histidine kinases. Light activation of the LOV domain leads to the formation of a flavin-cysteinyl adduct, which is the photoreceptor-signaling state that activates the kinase domain. Light-activated LOV-histidine kinases were found in two important plant and animal pathogens and in a marine photosynthetic bacterium and indicate that the LOV-histidine kinases are an important family of bacterial photosensory receptors.
T. E. Swartz, T.-S. Tseng, M. A. Frederickson, G. Paris, D. J. Comerci, G. Rajashekara, J.-G. Kim, M. B. Mudgett, G. A. Splitter, R. A. Ugalde, F. A. Goldbaum, W. R. Briggs, R. A. Bogomolni, Blue-light-activated histidine kinases: Two-component sensors in bacteria. Science 317, 1090-1093 (2007). [Abstract] [Full Text]