Functional and structural characterization of bacterial blue-light sensitive photoreceptors

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Sequence motifs encoding blue-light sensitive photoreceptors with high similarity to their plant counterparts have been identified in many prokaryote genomes. This resemblance was found also for several heterologously expressed gene products that show the phototropin-typical spectroscopic reactions. However, besides similarities, significant differences in the light-driven kinetics were detected. In contrast to the plant protomers, the prokaryote phototropin-related proteins are more prone to full-length expression. This allows an access to the study of the light induced signal transduction, since many of these receptors carry - besides the chromophore-binding motif - a histidine kinase domain in their C-terminal part that interacts with similarly present CheY-like response regulators, making them new members of a blue light-driven bacterial two-component signal transduction system. The spectroscopic properties of the Bacillus protein YtvA have already been described by us, however, there is strong demand for a more precise analysis, including the generation of mutants and a study of its behavior in the homologous system. Structure determination experiments by protein crystallization have been initiated.