Calcium-regulated photoproteins of marine coelenterates

Calcium-regulated photoproteins are bioluminescent proteins that are responsible for the luminescence of marine coelenterates. A photoprotein molecule is a stable enzyme-substrate complex consisting of a single polypeptide chain and an oxygen-preactivated substrate, 2-hydroperoxcoelenterazine, which is tightly but noncovalently bound with the protein. Bioluminescence is triggered by Ca2+ and results from decarboxylation of the substrate bound with the protein. This review considers the current information about the structure of photoproteins, the mechanism of the bioluminescent reaction, the function of particular amino acid residues of the active center in catalysis and the formation of the emitter, and the use of photoproteins in bioluminescent microanalysis.