Dinoflagellates are single-celled algae found in world's oceans. They are responsible
for the beautiful blue "phosphorescence" of the sea, which is in reality bioluminescence.
To the right is a scanning electron micrograph of Lingulodinium polyedrum.
To the left is the structure of the D3 domain luciferase from this organism.
Each of the 3 domains that make up this luciferase is able to produce
light individually. The reaction they catalyze is shown here:
Dinoflagellates are able to control their discreet light flashes by modulating hydrogen ion concentration in the organelles that contain the proteins associated with light production. Luciferase is inactive above pH 8 and the luciferin is sequestered by another protein. As hydrogen ions are allowed to enter the cell and the pH drops to 6.3, luciferin is released and reacts with the luciferase. The light cycle is also influenced by the circadian cycle of the dinoflagellates, with luciferase production only occurring at night.