Measurements of Photoreaction and Kinase Activity of Phototropin, a Photoreceptor Protein for Tropic Response in Plants: Involvement of Kinase Activity in the Photosensitivity of Tropic Response
Phototropin is a photoreceptor protein responsible for phototropic responses in plants. A phototropin molecule has two photoreceptive domains named LOV1 and LOV2 in the N-terminal region. Blue light absorbed by a chromophore in these domains triggers conformational changes in the protein moiety. The C-terminal region of phototropin forms a Ser/Thr kinase that is activated by these conformational changes. The activated phototropin kinase transmits signals downstream leading to tropic responses. The lifetime of the activated state may concern the sensitivity of the tropic responses to light. Thus, spectrophotometric and kinase activity analyses of phototropin are important to understand the light signaling processes related to the photosensitivity. The preparation of polypeptide samples of Arabidopsis phototropin and the methods of spectroscopic measurements and kinase assay of these samples are shown in this chapter.
Key wordsKinase assay LOV domain Photoreaction Phototropin Ser/Thr kinase Spectrophotometry
This work was supported in part by Grant-in-Aid for Scientific Research on Innovative Areas to S.T. (22120005) and Grant-in-Aid for Scientific Research on Priority Areas to S.T. (17084008) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan, and Grant-in-Aid for Exploratory Research to S.T. (23657105) and Grant-in-aid for Young Scientist B to K.O. (15K18559) from the Japan Society for the Promotion of Science.
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