23 オワンクラゲ生物発光機構に関する生物有機化学的研究(口頭発表の部)

抄録

Our research has been focusing on the molecular mechanism of a luminous jellyfish, Aequorea aequorea. This jellyfish has a photoprotein (aequorin), which contains coelenterazine (CL) as a chromophore. The chromophore exists as an imidazopyrazinone peroxide as comfirmed by X-ray crystallography studies by Shimomura. We have tried to perform a dynamic analysis of CL, which is only observed on the surface of aequorin. Upon photolysis of the hydroperoxide in aequorin, we found several oxidation points. These modified sites were analyzed by using nano-LC-ESI-ion-trap (IT) -MSn using our pre-packed gradient (PPG) solvent elution program. Peptide fragnets resulting from trypsin digests of aequorin and photo-irradiated aequorin were compared. The nano-LC-ESI-IT-MSn analysis provided three modified peptides. We found that three peptide fragments (T20, T21 and T22) of aequorin disappeared in the mass spectra after photolysis. We also found that Cys residues in T20, T21 and T22 of aequorin were converted to oxidized dithiothreitol adducts. We concluded that photolysis of reconstituted aequorin generated a reactive oxygen specie, which modify only Cys residues locating nearby the peroxide moiety of the chromophore.