title: Oxygen activation of apo-obelin-coelenterazine complex.
abstract: Ca(2+) -regulated photoproteins use a noncovalently bound 2-hydroperoxycoelenterazine ligand to emit light in response to Ca(2+) binding. To better understand the mechanism of formation of active photoprotein from apoprotein, coelenterazine and molecular oxygen, we investigated the spectral properties of the anaerobic apo-obelin-coelenterazine complex and the kinetics of its conversion into active photoprotein after exposure to air. Our studies suggest that coelenterazine bound within the anaerobic complex might be a mixture of N7-protonated and C2(-) anionic forms, and that oxygen shifts the equilibrium in favor of the C2(-) anion as a result of peroxy anion formation. Proton removal from N7 and further protonation of peroxy anion and the resulting formation of 2-hydroperoxycoelenterazine in obelin might occur with the assistance of His175. It is proposed that this conserved His residue might play a key role both in formation of active photoprotein and in Ca(2+) -triggering of the bioluminescence reaction.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
authors.forename: Elena V
authors.initials: EV
authors.lastname: Eremeeva
authors.forename: Pavel V
authors.initials: PV
authors.lastname: Natashin
authors.forename: Lei
authors.initials: L
authors.lastname: Song
authors.forename: Yuguang
authors.initials: Y
authors.lastname: Zhou
authors.forename: Willem J H
authors.initials: WJ
authors.lastname: van Berkel
authors.forename: Zhi-Jie
authors.initials: ZJ
authors.lastname: Liu
authors.forename: Eugene S
authors.initials: ES
authors.lastname: Vysotski
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D006639:Histidine / Q000737:chemistry / Q000378:metabolism; D037402:Hydrozoa / Q000737:chemistry / Q000378:metabolism*; D007093:Imidazoles / Q000737:chemistry / Q000378:metabolism*; D049449:Luminescence; D008164:Luminescent Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D010100:Oxygen / Q000378:metabolism*; D011485:Protein Binding; D011522:Protons; D011719:Pyrazines / Q000737:chemistry / Q000378:metabolism*; D013053:Spectrophotometry
chemical_list: D007093:Imidazoles; D008164:Luminescent Proteins; D011522:Protons; D011719:Pyrazines; C010497:obelin; C017144:coelenterazine; D006639:Histidine; D010100:Oxygen; D002118:Calcium