Abstract
Phototropin acts as a blue-light receptor for tropic responses, reorientation of chloroplasts, and stomata opening in plants, that are deeply concerned in the regulation of the efficiency of photosynthesis. Phototropin has two chromophoric domains named LOV (light, oxygen, voltage) 1 and 2, each of which bears a FMN, in its N-terminal half. C-terminal half is a serine/threonine kinase. Absorption of photon initiates photochemical reactions of FMN that may induce conformational changes in the protein moieties responsible for the regulation of kinase activity. Neither its molecular mechanism, nor the substrates for this kinase activity, except for phototropin itself, is known. We have started biophysical and biochemical analyses to clear them. The molecular mechanism by which the blue-photon energy induces conformational changes in the remote domain and the possibility of kinase activities on the other substrates than phototopin will be discussed.
