1 research outputs found
Photoadduct Formation from the FMN Singlet Excited State in the LOV2 Domain of Chlamydomonas reinhardtii Phototropin
The
two light, oxygen, and voltage domains of phototropin are blue-light
photoreceptor domains that control various functions in plants and
green algae. The key step of the light-driven reaction is the formation
of a photoadduct between its FMN chromophore and a conserved cysteine,
where the canonical reaction proceeds through the FMN triplet state.
Here, complete photoreaction mapping of CrLOV2 from Chlamydomonas reinhardtii phototropin and AsLOV2
from Avena sativa phototropin-1 was
realized by ultrafast broadband spectroscopy from femtoseconds to
microseconds. We demonstrate that in CrLOV2, a direct photoadduct
formation channel originates from the initially excited singlet state,
in addition to the canonical reaction through the triplet state. This
direct photoadduct reaction is coupled by a proton or hydrogen transfer
process, as indicated by a significant kinetic isotope effect of 1.4
on the fluorescence lifetime. Kinetic model analyses showed that 38%
of the photoadducts are generated from the singlet excited state