Dynamics of the amino-terminal and carboxyl-terminal helices of Arabidopsis phototropin 1 LOV2 studied by the transient grating.
Recently, conformational changes of the amino-terminal helix (A'α helix), in addition to the reported conformational changes of the carboxyl-terminal helix (Jα helix), have been proposed to be important for the regulatory function of the light-oxygen-voltage 2 domain (LOV2) of phototropin 1 from Arabidopsis. However, the reaction dynamics of the A'α helix have not been examined. Here, the unfolding reactions of the A'α and Jα helices of the LOV2 domain of phototropin 1 from Arabidopsis thaliana were investigated by the time-resolved transient grating (TG) method. A mutant (T469I mutant) that renders the A'α helix unfolded in the dark state showed unfolding of the Jα helix with a time constant of 1 ms, which is very similar to the time constant reported for the wild-type LOV2-linker sample. Furthermore, a mutant (I608E mutant) that renders the Jα helix unfolded in the dark state exhibited an unfolding process of the A'α helix with a time constant of 12 ms. On the basis of these experimental results, it is suggested that the unfolding reactions of these helices occurs independently.
Department of Chemistry, Graduate School of Science, Kyoto University , Kitashirakawa, Kyoto 606-8502, Japan.
Kimitoshi
K
Takeda
Yusuke
Y
Nakasone
Kazunori
K
Zikihara
Satoru
S
Tokutomi
Masahide
M
Terazima
D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002942:Circular Dichroism; D009154:Mutation; D056949:Phototropins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D013997:Time Factors
D029681:Arabidopsis Proteins; D056949:Phototropins