Computational Modeling Reveals the Mechanism of Fluorescent State Recovery in the Reversibly Photoswitchable Protein Dreiklang

• Published in: The journal of physical chemistry. B Vol. 123; no. 42; pp. 8901 - 8909
• Main Authors: Grigorenko, Bella L, Polyakov, Igor V, Krylov, Anna I, Nemukhin, Alexander V
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 24.10.2019
• Subjects: chemical reactions; fluorescence; molecular models; physical chemistry; quantum mechanics
• ISSN: 1520-6106; 1520-5207; 1520-5207
• DOI: 10.1021/acs.jpcb.9b06988

The unique properties of the photoswitchable protein Dreiklang are attributed to a reversible hydration/dehydration reaction at the imidazolinone ring of the chromophore. Recovery of the fluorescent state, which is associated with a chemical reaction of the chromophore’s dehydration, is an important part of the photocycle of this protein. Here we characterize the fluorescent (ON) and nonfluorescent (OFF) states of Dreiklang and simulate the thermal recovery reaction OFF → ON using computational approaches. By using molecular modeling methods including the quantum mechanics/molecular mechanics (QM/MM) technique, we characterize the structures and spectra of the ON- and OFF-states. The results are consistent with available experimental data. The computed reaction profile explains the observed recovery reaction and clarifies the mechanism of chemical transformations in the chromophore-containing pocket in Dreiklang.