title: Photochemical Reactions of the LOV and LOV-Linker Domains of the Blue Light Sensor Protein YtvA.
abstract: YtvA is a blue light sensor protein composed of an N-terminal LOV (light-oxygen-voltage) domain, a linker helix, and the C-terminal sulfate transporter and anti-σ factor antagonist domain. YtvA is believed to act as a positive regulator for light and salt stress responses by regulating the σB transcription factor. Although its biological function has been studied, the reaction dynamics and molecular mechanism underlying the function are not well understood. To improve our understanding of the signaling mechanism, we studied the reaction of the LOV domain (YLOV, amino acids 26-127), the LOV domain with its N-terminal extension (N-YLOV, amino acids 1-127), the LOV domain with its C-terminal linker helix (YLOV-linker, amino acids 26-147), and the YLOV domain with the N-terminal extension and the C-terminal linker helix (N-YLOV-linker, amino acids 1-147) using the transient grating method. The signals of all constructs showed adduct formation, thermal diffusion, and molecular diffusion. YLOV showed no change in the diffusion coefficient (D), while the other three constructs showed a significant decrease in D within ∼70 μs of photoexcitation. This indicates that conformational changes in both the N- and C-terminal helices of the YLOV domain indeed do occur. The time constant in the YtvA derivatives was much faster than the corresponding dynamics of phototropins. Interestingly, an additional reaction was observed as a volume expansion as well as a slight increase in D only when both helices were included. These findings suggest that although the rearrangement of the N- and C-terminal helices occurs independently on the fast time scale, this change induces an additional conformational change only when both helices are present.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University , Kyoto, Japan.
authors.forename: Seokwoo
authors.initials: S
authors.lastname: Choi
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University , Kyoto, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Nakasone
authors.affiliation: Molecular Microbial Physiology Group, Swammerdam Institute for Life Sciences, University of Amsterdam , 1090 GE Amsterdam, The Netherlands.
authors.forename: Klaas J
authors.initials: KJ
authors.lastname: Hellingwerf
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University , Kyoto, Japan.
authors.forename: Masahide
authors.initials: M
authors.lastname: Terazima
mesh_terms: D001412:Bacillus subtilis / Q000378:metabolism* / Q000528:radiation effects; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D002942:Circular Dichroism; D007700:Kinetics; D008027:Light; D008958:Models, Molecular; D010777:Photochemistry; D020283:Photoreceptors, Microbial / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D000072417:Protein Domains
chemical_list: D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial