{Reference Type}: Journal Article
{Title}: Green/red light-sensing mechanism in the chromatic acclimation photosensor.
{Author}: Nagae T;Fujita Y;Tsuchida T;Kamo T;Seto R;Hamada M;Aoyama H;Sato-Tomita A;Fujisawa T;Eki T;Miyanoiri Y;Ito Y;Soeta T;Ukaji Y;Unno M;Mishima M;Hirose Y;
{Journal}: Sci Adv
{Volume}: 10
{Issue}: 24
{Year}: 2024 Jun 14
{Factor}: 14.957
{DOI}: 10.1126/sciadv.adn8386
{Abstract}: Certain cyanobacteria alter their photosynthetic light absorption between green and red, a phenomenon called complementary chromatic acclimation. The acclimation is regulated by a cyanobacteriochrome-class photosensor that reversibly photoconverts between green-absorbing (Pg) and red-absorbing (Pr) states. Here, we elucidated the structural basis of the green/red photocycle. In the Pg state, the bilin chromophore adopted the extended C15-Z,anti structure within a hydrophobic pocket. Upon photoconversion to the Pr state, the bilin is isomerized to the cyclic C15-E,syn structure, forming a water channel in the pocket. The solvation/desolvation of the bilin causes changes in the protonation state and the stability of π-conjugation at the B ring, leading to a large absorption shift. These results advance our understanding of the enormous spectral diversity of the phytochrome superfamily.