Stability of dimer and domain-domain interaction of Arabidopsis phototropin 1 LOV2.
Transient grating signals after photoexcitation of Arabidopsis phototropin 1 light-oxygen-voltage 2 (phot1LOV2) domain without the linker were found to be very sensitive to temperature. In particular, the diffusion signal drastically increased with rising temperature. The signal was consistently explained by the superposition of the photo-induced dissociation and association reactions. This observation indicated the presence of an equilibrium between the monomer and dimer forms of the phot1LOV2 domain in the dark. The equilibrium was confirmed by a gel chromatographic technique. The equilibrium constants at various temperatures were calculated from the fraction of the dimer, and the stabilization enthalpy and entropy were determined. Interestingly, the transient grating signal of phot1LOV2 with the linker (phot1LOV2-linker), which exists as the monomer form, was also temperature dependent; the diffusion signal intensity decreased with increasing temperature. Because the diffusion signal reflects a conformation change of the linker upon photoexcitation, this temperature dependence indicated that there were two forms of the phot1LOV2-linker. One form exhibited a conformational change upon photoexcitation whereas the other form showed no change. These two forms are not distinguishable spectroscopically. The fraction of these species depended on the temperature. Considering the monomer-dimer equilibrium of the phot1LOV2 domain, we suggest that the nonreactive form possesses the linker region that is dissociated from the LOV2 domain. Because the dissociation of the linker region from the LOV2 domain is a key step for the conformation change of the phot1LOV2-linker to induce biological activity, we proposed that the phototropins could have a role as a temperature sensor.
Nakasone
Yusuke
Y
Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan.
Eitoku
Takeshi
T
Zikihara
Kazunori
K
Matsuoka
Daisuke
D
Tokutomi
Satoru
S
Terazima
Masahide
M
D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002942:Circular Dichroism; D019281:Dimerization; D007834:Lasers; D008027:Light; D010750:Phosphoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D020836:Protein Structure, Quaternary; D015398:Signal Transduction / Q000502:physiology*; D013696:Temperature
D029681:Arabidopsis Proteins; D010750:Phosphoproteins; C103646:NPH1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases