Abstract
Phototropins, blue light receptors in plants, have two photosensory domains named LOV which bind FMN as a chromophore. We have studied the light-induced structural changes of LOV domains of Adiantum phytochrome3 (phy3) by means of low temperature FTIR spectroscopy. In order to identify IR signals, isotope-labeled LOV2 domains were prepared.
The reconstitution of [2-13C]FMN revealed that the hydrogen-bonding of C(2)=O group in FMN was weakened. The reconstitution of [1,3-15N2]FMN revealed that N(3)-H group of FMN formed very strong hydrogen bond in the unphotolyzed state and stronger hydrogen bond upon the formation S390 intermediate. We could reveal the change of the hydrogen-bonding network between FMN and surrounding amino acid side chains. The changes of such hydrogen-bonding network may be more important than the direct change of adduct formation for the structural change in the α-helix and β-sheet regions.
