Symplectin bioluminescence

R653 M. Isobe, M. Kuse, T. Fujii, H. Takahashi, K. Ohshima, H. Mori, J.-Y. Ahn and M. Tsukasa, Molecular Mechanisms of Bioluminescence of Symplectin, a Photoprotein from Okinawan Squid, Symplectoteuthis Oualaniensis L , Tennen Yuki Kagobutsu Toronkai Koen Yoshishu, 2000, 42, 97... 

Now we focus on the structural analysis of symplectin active site and the molecular mechanism of symplectin bioluminescence. ... 

From the sequence analysis of symplectin with LC-Q-TOF-MS, MS/MS and cDNA, symplectin has 501 amino acids sequence. Partial degradation of symplectin with trypsin afforded a 40 kDa protein (symplectin A ), which is the C-terminal part of symplectin and still has bioluminescent activity. We suppose that the active site of symplectin exists in the 40 kDa symplectin A. ... 

C-labeled DCT analog C C-DCTa) was synthesized to prove the chromophoric structure of symplectin. Dithiothreitol and glutathione (apo-symplectin models) reacted with C-DCTa to afford the luminescent active chromophores, which were analyzed with NMR and MS. We demonstrated that DCT binds with the sulfhydryl residues at the 2 - C-labeled carbon as shown in Fig. 2, and we succeeded in reproducing a model symplectin bioluminescence with C-DCTa. ... 

Now we investigate the symplectin active site by using a photoaffinity labeling and the nano-LC-Q-TOF-MS analysis and also study the structure and activity relationship (SAR) between DCT structures and symplectin bioluminescent activities. For the SAR study, we also developed a novel synthetic method for DCT analogs. ... 

Working hypothesis. We now postulate that the absolute configuration of the chromophore in the symplectin active site might be important based on these results. Although both substrate (DCL) and product (amide compound and coelenteramine) have no chirality (Fig. 1), we now assume that dynamic chirality of the active site could play an important role in bioluminescence. We are now trying to analyze the reaction products in order to answer the question why diF-DCLs have different activity. 

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