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Concerted Asynchronous Hula‐Twist Photoisomerization in the S65T/H148D Mutant of Green Fluorescent Protein
Author(s) -
Zhang Qiangqiang,
Chen Xuebo,
Cui Ganglong,
Fang WeiHai,
Thiel Walter
Publication year - 2014
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201405303
Subject(s) - fluorescence , photoisomerization , quantum yield , photochemistry , green fluorescent protein , chemistry , mutant , qm/mm , biophysics , molecular dynamics , computational chemistry , isomerization , physics , optics , biochemistry , catalysis , biology , gene
Fluorescence emission of wild‐type green fluorescent protein (GFP) is lost in the S65T mutant, but partly recovered in the S65T/H148D double mutant. These experimental findings are rationalized by a combined quantum mechanics/molecular mechanics (QM/MM) study at the QM(CASPT2//CASSCF)/AMBER level. A barrierless excited‐state proton transfer, which is exclusively driven by the Asp148 residue introduced in the double mutant, is responsible for the ultrafast formation of the anionic fluorescent state, which can be deactivated through a concerted asynchronous hula‐twist photoisomerization. This causes the lower fluorescence quantum yield in S65T/H148D compared to wild‐type GFP. Hydrogen out‐of‐plane motion plays an important role in the deactivation of the S65T/H148D fluorescent state.