Reaction mechanism of the bioluminescent protein mnemiopsin1 revealed by X-ray crystallography and QM/MM simulations

Abstract

Bioluminescence of a variety of marine organisms, mostly cnidarians and ctenophores, is carried out by Ca2-dependent photoproteins. The mechanism of light emission operates via the same reaction in both animal families. Despite numerous studies on the ctenophore photoprotein family, the detailed catalytic mechanism and arrangement of amino acid residues surrounding the chromophore in this family are a mystery. Here, we report the crystal structure of Cd2-loaded apo-mnemiopsin1, a member of the ctenophore family, at 2.15 Å resolution and used quantum mechanics/molecular mechanics (QM/MM) to investigate its reaction mechanism. The simulations suggested that an Asp-156 –Arg-39 –Tyr-202 triad cr..