title: Molecular mechanism of Symplectoteuthis bioluminescence--part 4: chromophore exchange and oxidation of the cysteine residue.
abstract: Symplectin is one of the few photoproteins, which forms covalent bonds with the dehydro-coelenterazine (DCL) at the binding sites and the active site. This binding takes place through the SH's of the cysteine residues via conjugate addition reaction. This photoprotein contains the chromophore molecules at the binding cites first, and then moves to the active cite Cys-390 for the luminescence. The current study focuses on these dynamic aspects of the chromophore using the natural photoprotein by analyzing the fluorescence changing of the DCL chromophores analogs with 8-(4'-methoxyphenyl)- or 8-(2'-naphthyl)-group and 2-(2',4'-difluorophenyl)-group. Exchanges of these chromophores were monitored the fluorescence at slightly acidic media and also from the luminescence function observed at the optimum pH 7.8. The non-fluorescent naphthyl analogs was even proven to make the covalent bond formation at pH 6.0 and evidently to obtain the corresponding luminescent product amide by liquid chromatographic detection from the spent solutions.
authors: Chemistry Department, National Tsing Hua University, 101, Sec. 2, Kuang Fu Road, Hsinchu 30013, Taiwan.
authors: Chun-Ming
authors: CM
authors: Chou
authors: Chemistry Department, National Tsing Hua University, 101, Sec. 2, Kuang Fu Road, Hsinchu 30013, Taiwan.
authors: Yu-Wen
authors: YW
authors: Tung
authors: Chemistry Department, National Tsing Hua University, 101, Sec. 2, Kuang Fu Road, Hsinchu 30013, Taiwan. Electronic address: minoru@mx.nthu.edu.tw.
authors: Minoru
authors: M
authors: Isobe
mesh_terms: D000818:Animals; D044482:Benzeneacetamides / Q000138:chemical synthesis / Q000737:chemistry; D001665:Binding Sites; D020134:Catalytic Domain; D049830:Cephalopoda / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000138:chemical synthesis / Q000737:chemistry; D007700:Kinetics; D037102:Lectins / Q000737:chemistry / Q000378:metabolism; D008163:Luminescent Measurements; D010084:Oxidation-Reduction; D011719:Pyrazines / Q000138:chemical synthesis / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet
chemical_list: D044482:Benzeneacetamides; D007093:Imidazoles; D037102:Lectins; D011719:Pyrazines; C542661:coelenteramide; C116816:dehydrocoelenterazine; D003545:Cysteine
keywords: Bioluminescence; Coelenterazine; Photoprotein; Symplectin