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Dynamic Chirality Determines Critical Roles for Bioluminescence in Symplectin–Dehydrocoelenterazine System
Author(s) -
Kongjinda Vorawan,
Nakashima Yosuke,
Tani Naoki,
Kuse Masaki,
Nishikawa Toshio,
Yu ChinHui,
Harada Nobuyuki,
Isobe Minoru
Publication year - 2011
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201100089
Subject(s) - stereocenter , chirality (physics) , chemistry , bioluminescence , chromophore , cysteine , luminescence , stereochemistry , covalent bond , residue (chemistry) , peptide , photoprotein , photochemistry , organic chemistry , biochemistry , enantioselective synthesis , enzyme , chiral symmetry breaking , physics , optoelectronics , quantum mechanics , quark , nambu–jona lasinio model , catalysis
Symplectin is a photoprotein containing the dehydrocoelenterazine (DCL) chromophore, which links to a cysteine residue through a covalent bond with the emission of blue light. This study focuses on the stereochemical process of the emerging stereogenic centers. Two isomeric fluorinated DCL analogs (2,4‐diF‐ and 2,6‐diF‐DCL) were employed owing to their different bioluminescence activities, these being 200 % and 20 % compared to natural DCL, respectively. Each of these diF‐DCLs was found to exchange with the natural DCL in symplectin at pH 6.0. The emerging stereogenic carbons were racemic at the binding sites. Changing the pH of this storage form to the protein’s optimum solubility pH (pH 7.8) resulted in 2,4‐diF‐DCL‐bound symplectin luminescence, and the spent solutions were then analyzed and coelenteramide‐390‐CGLK‐peptide and coelenteramine were detected after a peptidase digestion. The same analysis of the 2,6‐diF‐DCL‐bound symplectin, on the other hand, afforded coelenteramine only but no coelenteramide. When the racemic storage diF‐DCLs moved to the active site at pH 7.8, a change in the chirality with the 390‐Cys residue resulted. Model experiments using L ‐cysteine‐containing CGLK‐peptide supported two diastereoisomers from each diF‐DCL. The significant difference in the luminescence from these two chromophores is attributed to a plausible mechanism including the dynamically variable stereogenic center emerging at the storage and then the active site on the symplectin. It is concluded that such dynamic chirality plays a significant role in the symplectoteuthis bioluminescence.