One of the joys of summer evenings is watching fireflies light up the night sky. These twinkling bugs communicate with one another using flashes of light — a trick biologists have appropriated to convey readouts from their experiments. Various forms of the enzyme responsible for the fireflies' luminescence — luciferase — can produce slightly different colours, ranging from red to yellow to green. Elsewhere in this issue, Toru Nakatsu et al. (Nature 440, 372–376; 2006) report several X-ray crystal structures of luciferase from the Japanese Genji-botaru firefly (Luciola cruciata, pictured) that explain how small changes in this protein can change the colour of the emitted light.
Single amino-acid changes in the active site of luciferase can alter the colour of the light emitted by the protein, but the chemical mechanism involved has been a mystery. Now Nakatsu et al. have obtained a series of ‘snapshots’ of the reaction — luciferase bound to the reactants (adenosine triphosphate and magnesium); an analogue of one of the reaction intermediates (known as DLSA); and the products (oxyluciferin and adenosine monophosphate).
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