Bioluminescence—i.e., the emission of visible light by living organisms—is defined as a biochemical reaction involving, at least, luciferin substrate, an oxygen derivative, and specialised luciferase enzyme. In some cases, enzyme substrate are durably associated form photoprotein. While this terminology is educatively useful to explain bioluminescence, it gives false idea that all luminous orga...

Ca(2+)-regulated photoproteins are responsible for the bioluminescence of a variety of marine organisms, mostly coelenterates. The photoproteins consist of a single polypeptide chain to which an imidazopyrazinone derivative (2-hydroperoxycoelenterazine) is tightly bound. According to photoprotein spatial structures the side chains of His175, Trp179, and Tyr190 in obelin and His169, Trp173, Tyr1...

Photoproteins, which emit light in an oxygen-independent intramolecular reaction initiated by calcium ions, have been isolated from several bioluminescent organisms, including the hydrozoan jellyfish Aequorea and the ctenophore Mnemiopsis. The system of a related anthozoan coelenterate, the sea pansy Renilla reniformis, however, is oxygen dependent, requiring two organic components, luciferin a...

Aequorin is a Ca(2+)-sensitive photoprotein isolated from the jellyfish Aequorea victoria. It is an ideal probe for measuring Ca(2+) concentration ([Ca(2+)]) in intracellular organelles because it can be modified to include specific targeting sequences. On the binding of Ca(2+) to three high-affinity sites in aequorin, an irreversible reaction occurs in which the prosthetic group coelenterazine...

The luminescent jellyfish Aequorea contains a photoprotein, aequorin, which emits light by an intramolecular reaction in the presence of a trace amount of Ca2+. A cDNA library of Aequorea was constructed and clones carrying the cDNA for the Ca2+-dependent photoprotein were isolated by the method of colony hybridization using synthetic oligonucleotide probes. The primary structure of the protein...

Aequorin is a Ca-sensitive photoprotein isolated from the jellyfish Aequorea victoria. It is an ideal probe for measuring Ca concentration ([Ca]) in intracellular organelles because it can be modified to include specific targeting sequences. On the binding of Ca to three high-affinity sites in aequorin, an irreversible reaction occurs in which the prosthetic group coelenterazine is released and...

Aequorin and obelin are photoproteins whose calcium controlled bioluminescent light emission is used for labeling in assays, for the determination of calcium concentrations in vivo, and as a reporter in cellular imaging. Both of these photoproteins emit blue light from a 2-hydroperoxycoelenterazine chromophore, which is non-covalently bound in the hydrophobic core of the proteins. In an effort ...

Analysis of substances involved in light-emitting reactions among bioluminescent coelenterates has revealed a pronounced uniformity in the structural features of initial reactants, i.e., "luciferins" and photo-protein chromophores, as well as the light-emitter product. This product is structurally identical among the different classes of coelenterates: Hydrozoa (the jellyfish, Aequorea), Anthoz...