title: Time-resolved fluctuation during the photochemical reaction of a photoreceptor protein: phototropin1LOV2-linker.
abstract: Although the relationship between structural fluctuations and reactions is important for elucidating reaction mechanisms, experimental data describing such fluctuations of reaction intermediates are sparse. In order to investigate structural fluctuations during a protein reaction, the compressibilities of intermediate species after photoexcitation of a phot1LOV2-linker, which is a typical LOV domain protein with the C-terminal linker including the J-α helix and used recently for optogenetics, were measured in the time-domain by the transient grating and transient lens methods with a high pressure optical cell. The yield of covalent bond formation between the chromophore and a Cys residue (S state formation) relative to that at 0.1 MPa decreased very slightly with increasing pressure. The fraction of the reactive species that yields the T state (linker-unfolded state) decreased almost proportionally with pressure (0.1-200 MPa) to about 65%. Interestingly, the volume change associated with the reaction was much more pressure sensitive. By combining these data, the compressibility changes for the short lived intermediate (S state) and the final product (T state) formation were determined. The compressibility of the S state was found to increase compared with the dark (D) state, and the compressibility decreased during the transition from the S state to the T state. The compressibility change is discussed in terms of cavities inside the protein. By comparing the crystal structures of the phot1LOV2-linker at dark and light states, we concluded that the cavity volumes between the LOV domain and the linker domain increase in the S state, which explains the enhanced compressibility.
authors: Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan. mterazima@kuchem.kyoto-u.ac.jp.
authors: Kunisato
authors: K
authors: Kuroi
authors: Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan. mterazima@kuchem.kyoto-u.ac.jp.
authors: Francielle
authors: F
authors: Sato
authors: Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan. mterazima@kuchem.kyoto-u.ac.jp.
authors: Yusuke
authors: Y
authors: Nakasone
authors: Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan.
authors: Kazunori
authors: K
authors: Zikihara
authors: Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan.
authors: Satoru
authors: S
authors: Tokutomi
authors: Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan. mterazima@kuchem.kyoto-u.ac.jp.
authors: Masahide
authors: M
authors: Terazima
mesh_terms: D029681:Arabidopsis Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004268:DNA-Binding Proteins / Q000737:chemistry*; D008027:Light; D008958:Models, Molecular; D010777:Photochemistry; D056949:Phototropins / Q000737:chemistry*; D011485:Protein Binding / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C000612094:LOV2 protein, Arabidopsis; D056949:Phototropins