Decoding bioluminescence in Keroplatinae: computational insights from inverse virtual screening and the transcriptome of Orfelia fultoni.

Bioluminescence is a natural occurrence found in a wide array of species, encompassing both marine and terrestrial life. Among the less-understood bioluminescent systems is the one found within the Keroplatinae subfamily, which may use riboflavin and a precursor of the 3-hydroxykynurenic acid as substrates to produce light. However, the luciferase and other proteins used to produce bioluminescence remain unknown. Here, we employed inverse virtual screening (IVS), utilizing the transcriptome of Orfelia fultoni, an organism within this subfamily. Our analysis led to the identification of 2868 theoretical structures. We identified 11 proteins that could be associated with the bioluminescent process, including hexamerin-like proteins, NADPH-cytochrome P450 reductase, heat shock protein HSP90, V-ATPase subunit A, and enzymes related to fatty acid metabolism. Further exploration unveiled a trimeric structure of hexamerins, showing binding interactions with riboflavin and 3-hydroxykynurenic acid. We proposed a mechanism for bioluminescence in O. fultoni, involving hexamerins and NADPH-cytochrome P450 reductase. This study enhances our understanding of bioluminescence, contributing to the broader field of evolutionary biology, emphasizing adaptations to specific environments.