Light-induced structural changes of LOV domain-containing polypeptides from Arabidopsis phototropin 1 and 2 studied by small-angle X-ray scattering.
Phototropin is a blue-light receptor of plants and comprises two light-receptive domains, LOV1 and LOV2, Ser/Thr kinase domain and one linker region connecting the LOV2 and the kinase domains. The LOV2 domain is thought to regulate predominantly the light-dependent autophosphorylation of the kinase domain, leading to cellular signaling cascades. In this study, we constructed recombinant LOV1, LOV2, and LOV2-linker polypeptides from phototropin 1 and phototropin 2 of Arabidopsis thaliana and studied their quaternary structures and light-dependent conformational changes by small-angle X-ray scattering. The molecular weights of the polypeptides determined from scattering intensities demonstrated the dimeric associations of LOV1 polypeptides of both isoforms. In contrast, while LOV2 and LOV2-linker polypeptides of phototropin 1 were homodimers, corresponding polypeptides of phototropin 2 existed as monomeric forms. Under blue-light irradiation, the LOV2-linker polypeptide of phototropin 1 displayed small but definite changes of the scattering profile. Through simulation of low-resolution molecular structures, the changes were likely explained as structural changes of the linker region and/or a movement of the region relative to the LOV2 domain. Light-induced profile changes were not observed in the Cys(512)Ala mutated LOV2-linker polypeptide of phototropin 1 losing the phototransformation capability. Thus, it was indicated that the photoreaction in the LOV2 domain probably caused the structural changes in the LOV2-linker polypeptide of phototropin 1. On the basis of the results, the interdomain interactions in phototropin are discussed.
Nakasako
Masayoshi
M
Department of Physics, Faculty of Science and Technology, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Kanagawa 223-8522, Japan. nakasako@phys.keio.ac.jp
Iwata
Tatsuya
T
Matsuoka
Daisuke
D
Tokutomi
Satoru
S
D000409:Alanine / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017360:Arabidopsis / Q000737:chemistry*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003198:Computer Simulation; D056931:Cryptochromes; D003545:Cysteine / Q000737:chemistry; D019281:Dimerization; D004926:Escherichia coli / Q000235:genetics; D005420:Flavoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D007700:Kinetics; D008027:Light; D008958:Models, Molecular; D008970:Molecular Weight; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D010777:Photochemistry; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary / Q000528:radiation effects*; D011994:Recombinant Proteins / Q000378:metabolism
D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D005420:Flavoproteins; D010455:Peptides; D020033:Protein Isoforms; D011994:Recombinant Proteins; D003545:Cysteine; D000409:Alanine