title: Imidazole-assisted catalysis of luminescence reaction in blue fluorescent protein from the photoprotein aequorin.
abstract: Blue fluorescent protein from the calcium-binding photoprotein aequorin (BFP-aq) is a dissociable complex of Ca(2+)-bound apoaequorin and coelenteramide, and is identified as a luciferase that catalyzes the oxidation of coelenterazine by molecular oxygen to emit light. Based on the chemical luminescence of coelenterazine oxidation by an acid-base mechanism, we found that the luminescence activity of BFP-aq was stimulated by imidazole at concentrations of 30-300mM with coelenterazine and its analogues. The kinetic analyses indicate that imidazole has no effect on the binding affinity of coelenterazine to BFP-aq and may act as a catalytic base, accepting a proton from the -NH- group of coelenterazine and stimulating luminescence activity.
authors.affiliation: Yokohama Research Center, Chisso Corporation, 5-1 Okawa, Kanazawa-ku, Yokohama 236-8605, Japan. sinouye@chisso.co.jp
authors.forename: Satoshi
authors.initials: S
authors.lastname: Inouye
authors.forename: Satoko
authors.initials: S
authors.lastname: Sasaki
mesh_terms: D000331:Aequorin / Q000378:metabolism*; D000577:Amides / Q000378:metabolism; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002384:Catalysis; D007093:Imidazoles / Q000378:metabolism*; D007700:Kinetics; D008156:Luciferases / Q000378:metabolism; D049408:Luminescent Agents / Q000494:pharmacology*; D008164:Luminescent Proteins / Q000378:metabolism; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D010100:Oxygen / Q000494:pharmacology; D011522:Protons; D011719:Pyrazines / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D000577:Amides; D007093:Imidazoles; D049408:Luminescent Agents; D008164:Luminescent Proteins; D011522:Protons; D011719:Pyrazines; C409504:blue fluorescent protein, Aequorea victoria; C017144:coelenterazine; D000331:Aequorin; D008156:Luciferases; D010100:Oxygen; D002118:Calcium