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H2O-Bridged Proton-Transfer Channel in Emitter Species Formation in Obelin Bioluminescence.

Shu-Feng ChenEugene S VysotskiYa-Jun Liu
Published in: The journal of physical chemistry. B (2021)
Bioluminescence of a number of marine organisms is conditioned by Ca2+-regulated photoprotein (CaRP) with coelenterazine as the reaction substrate. The reaction product, coelenteramide, at the first singlet excited state (S1) is the emitter of CaRP. The S1-state coelenteramide is produced via the decomposition of coelenterazine dioxetanone. Experiments suggested that the neutral S1-coelenteramide is the primary emitter species. This supposition contradicts with theoretical calculations showing that the anionic S1-coelenteramide is a primary product of the decomposition of coelenterazine dioxetanone. In this study, applying molecular dynamic (MD) simulations and the hybrid quantum mechanics/molecular mechanics (QM/MM) method, we investigated a proton-transfer (PT) process taking place in CaRP obelin from Obelia longissima for emitter formation. Our calculations demonstrate a concerted PT process with a water molecule as a bridge between anionic S1-coelenteramide and the nearest histidine residue. The low activation barrier as well as the strong hydrogen-bond network between the proton donor and the proton acceptor suggests a fast PT process comparable with that of the lifetime of excited anionic S1-coelenteramide. The existence of the PT process eliminates the discrepancy between experimental and theoretical studies. The fast PT process at emitter formation can also take place in other CaRPs.
Keyphrases
  • electron transfer
  • molecular dynamics
  • energy transfer
  • monte carlo
  • light emitting
  • molecular dynamics simulations
  • transcription factor
  • mass spectrometry
  • quantum dots
  • atomic force microscopy
  • solar cells