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What role does green fluorescent protein play in the light of Aequorea victoria?

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time-lapse photo of fireflies — Bioluminescence Time-lapse image of fireflies in the Catskill Mountains, New York. Firefly light is a cold light, with approximately 100 percent of the energy given off as light and only a minute amount as heat. Only light in the visible spectrum is emitted.

In the jellyfish Aequorea victoria, the green fluorescent protein (GFP) does not function as the primary light-emitting enzyme in a standard luciferin-luciferase reaction. Instead, the jellyfish produces light through a separate bioluminescent protein called [aequorin].12

When aequorin binds with calcium ions, it undergoes a chemical reaction that emits blue light. GFP acts as a secondary component in this process: it absorbs the blue light emitted by aequorin and re-emits it as green fluorescence through a process known as energy transfer. While the primary bioluminescence is triggered by the calcium-dependent aequorin reaction, GFP is responsible for the characteristic green glow observed in the organism.23

Scientists have since utilized GFP as a vital tool in biological research, as it can be expressed in other organisms to act as a visual marker for tracking protein activity and cellular processes.3