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Issue 7, 2019
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Tuning the fluorescence of calcium-discharged photoprotein obelin via mutating at the His22-Phe88-Trp92 triad – a QM/MM study

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Abstract

The fluorescence (FL) of calcium-discharged photoprotein (CaDP) can be altered by easily mutating CaDP without modifying coelenteramide (CLM), which is the decarboxylation product of coelenterazine in calcium-regulated photoprotein. The His22-Phe88-Trp92 triad (the ordering numbers of three amino acids are sorted by a crystal structure (PDB: 2F8P) of calcium-discharged obelin, i.e., CaDP-obelin) is closely related to CaDP-obelin FL, since it exists in close proximity to the 5-p-hydroxyphenyl of CLM. Therefore, it is important to thoroughly investigate how the mutations of this triad affect the emission color of CaDP-obelin FL. In this study, by mutating wild-type CaDP-obelin (WT) at the His22-Phe88-Trp92 triad, we theoretically constructed its nine mutants of separable FL colors. Through combined quantum mechanics and molecular mechanics (QM/MM) calculations and molecular dynamics (MD) simulations, the influence of the mutations of this triad on the CaDP-obelin FL was analyzed considering the H-bond effect and the charge effect. This study demonstrated that the mutations at the His22-Phe88-Trp92 triad redistribute the charges on the Dπ-A molecule, CLM, change the charge transfer from the D to the (π + A) moiety, and thereby alter the FL emission. Appending more negative charges on the phenolate moiety of CLM benefits the FL redshift.

Graphical abstract: Tuning the fluorescence of calcium-discharged photoprotein obelin via mutating at the His22-Phe88-Trp92 triad – a QM/MM study

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Article information


Submitted
21 Apr 2019
Accepted
30 May 2019
First published
31 May 2019

Photochem. Photobiol. Sci., 2019,18, 1823-1832
Article type
Paper

Tuning the fluorescence of calcium-discharged photoprotein obelin via mutating at the His22-Phe88-Trp92 triad – a QM/MM study

M. Gao, B. Ding and Y. Liu, Photochem. Photobiol. Sci., 2019, 18, 1823
DOI: 10.1039/C9PP00191C

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