The interplay between chromophore and protein determines the extended excited state dynamics in a single-domain phytochrome
Chavdar Slavov, Tobias Fischer, Avishai Barnoy, Heewhan Shin, Aditya G. Rao, Christian Wiebeler, Xiaoli Zeng, Yafang Sun, Qian-Zhao Xu, Alexander Gutt, Kai‐Hong Zhao, Wolfgang Gärtner, Xiaojing Yang, Igor Schapiro, Josef Wachtveitl
Abstract
form as well as the formation of the primary photoproduct Lumi-R using time-resolved spectroscopy and hybrid quantum mechanics/molecular mechanics simulations. We show that the unusually long excited state lifetime (broad lifetime distribution centered at ∼300 picoseconds) is due to the interactions between the isomerizing pyrrole ring D and an adjacent conserved Tyr142. The decay kinetics shows a strongly distributed character which is imposed by the nonexponential protein dynamics. Our findings offer a mechanistic insight into how the quantum efficiency of the bilin photoisomerization is tuned by the protein environment, thereby providing a structural framework for engineering bilin-based optical agents for imaging and optogenetics applications.