Abstract
Phototropin (phot), a blue light sensor in plants, has two photoreceptive domains named LOV1 and LOV2, and Ser/The kinase domain. phot is thought to be a blue-light-regulated protein kinase in which LOV2 acts as a molecular switch of the photoregulation and LOV1 is involved in the regulation of the photosensitivity. In addition, LOV1 is reported to act as a dimer forming site. Then, we studied the molecular basis of the LOV1 dimerization in Arabidopsis phot1 and 2, and obtained the two results. 1) Dimeric crystal structures of both the LOV1 have been solved. phot1-LOV1 forms a dimer by interfacing each β-scaffold in an antiparallel manner and forming a S-S bond. In contrast, phot2-LOV1 dimer cannot form the S-S bond and dimerizes mainly through hydrogen-bonding. 2) Reduction of S-S bond monomerized phot1-LOV1 dimer and two amino acid substitutions involved in the dimer formation resulted in monmerization of phot2-LOV1.
