14-3-3 proteins are luciferases candidate proteins from lanternfish Diaphus watasei

The lanternfish is a deep-sea fish with ventral-lateral and head photophores. It uses its ventral-lateral photophores to camouflage its ventral silhouette, a strategy called counterillumination. The bioluminescent reaction of lanternfish involves coelenterazine as a substrate luciferin but the enzyme catalyzing the bioluminescent reaction has not been identified. We report a candidate enzyme of luciferase from lanternfish Diaphus watasei. We purified the luciferase and performed SDS-PAGE analysis resulted in two bands corresponding to the activity, and following mass spectrometry analysis detected three 14-3-3 proteins of which functions is known to exhibit protein-protein interactions. The molecular weights and isoelectric points of the 14-3-3 proteins were almost consistent with the luciferase properties. The addition of two 14-3-3 binding compounds, R18 peptide and fusicoccin, resulted in the inhibition of the luciferase activity. However, the two 14-3-3 recombinant proteins showed very slight luminescence activity. These results suggested that the 14-3-3 proteins are candidate luciferases of D. watasei.