title: A PixD--PapB chimeric protein reveals the function of the BLUF domain C-terminal α-helices for light signal transduction.
abstract: Blue light-using flavin (BLUF) proteins form a subfamily of blue light photoreceptors, are found in many bacteria and algae, and are further classified according to their structures. For one type of BLUF-containing protein, e.g. PixD, the central axes of its two C-terminal α-helices are perpendicular to the β-sheet of its N-terminal BLUF domain. For another type, e.g. PapB, the central axes of its two C-terminal α-helices are parallel to its BLUF domain β-sheet. However, the functional significance of the different orientations with respect to phototransduction is not clear. For the study reported herein, we constructed a chimeric protein, Pix0522, containing the core of the PixD BLUF domain and the C-terminal region of PapB, including the two α-helices, and characterized its biochemical and spectroscopic properties. Fourier transform infrared spectroscopy detected similar light-induced conformational changes in the C-terminal α-helices of Pix0522 and PapB. Pix0522 interacts with and activates the PapB-interacting enzyme, PapA, demonstrating the functionality of Pix0522. These results provide direct evidence that the BLUF C-terminal α-helices function as an intermediary that accepts the flavin-sensed blue light signal and transmits it downstream during phototransduction.
authors: Center for Biological Resources and Informatics, Tokyo Institute of Technology, Yokohama, 226-8501 Japan.
authors: Shukun
authors: S
authors: Ren
authors: Masahiro
authors: M
authors: Sawada
authors: Koji
authors: K
authors: Hasegawa
authors: Yoshihiro
authors: Y
authors: Hayakawa
authors: Hiroyuki
authors: H
authors: Ohta
authors: Shinji
authors: S
authors: Masuda
mesh_terms: D000595:Amino Acid Sequence; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D005415:Flavins / Q000737:chemistry*; D055537:Light Signal Transduction; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry* / Q000378:metabolism*; D016415:Sequence Alignment; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship
chemical_list: D005415:Flavins; D011994:Recombinant Proteins; C038134:blue flavin; D010727:Phosphoric Diester Hydrolases