THE POLYPEPTIDE COMPONENTS OF SCINTILLONS, THE BIOLUMINESCENCE ORGANELLES OF THE DINOFLAGELLATE GONYAULAX-POLYEDRA

Scintillons, the bioluminescence organelles of Gonyaulax polyedra, wer e purified by isopycnic density gradient centrifugation until only low levels of contaminating chloroplasts and mitochondria were detected b y fluorescence and electron microscopy. Purified scintillons catalyzed the luminescent reaction with kinetics identical to those observed du ring the bioluminescence flash in vivo. Polyacrylamide gel electrophor esis in the presence of sodium dodecyl sulfate indicated that the orga nelles appeared to contain only two proteins. These proteins were iden tified as luciferase (135 kilodaltons) and luciferin-binding protein ( 75 kilodaltons) based on their size and their known functions in the b ioluminescence reaction in vitro. The staining of luciferin-binding pr otein by Coomassie blue was 2.4 +/- 0.3 (n = 19) times greater than th e luciferase, suggesting that there are four binding protein monomers for every luciferase monomer. A model is proposed for the close packin g of the two proteins inside the scintillons.