抄録
Phototropin has two chromophoric domains named LOV1 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. To investigate the details of the early photoreception process, we have started biophysical analyses using UV-visible absorption, FT-IR and CD spectra of the LOV domains. We have already reported that the thiol-flavin adduct but not thiolate-flavin (Schwartz et al., 2001) adduct is formed between C4a of the isoalloxazine ring of FMN and thiol of the only one cystein in the LOV. In the present paper, we will show the adduct formation induces significant conformational changes in the protein moieties of phototropin in contrast to the figure obtained by X-ray crystallography with little conformational change in them.
