Structural basis for the emission of violet bioluminescence from a W92F obelin mutant |
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Authors: | Deng L Vysotski E S Liu Z J Markova S V Malikova N P Lee J Rose J Wang B C |
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Institution: | Department of Chemistry, University of Georgia, Athens 30602, USA. ldeng@sunchem.chem.uga.edu |
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Abstract: | Mutation of the Trp92 that is known to lie within the active site of the photoprotein obelin from Obelia longissima, results in a shift of the bioluminescence color from blue (lambda(max)=485 nm) to violet. The corrected spectrum shows a new band with lambda(max)=410 nm now contributing equally to the one at longer wavelength. The crystal structure of this W92F obelin determined at 1.72 A resolution shows that there is no significant change in the dimensions of the active site between WT obelin (recombinant Ca2+-regulated photoprotein from Obelia longissima) and the mutant. It is proposed that the bioluminescence spectral shift results from removal of a hydrogen bond from the indole of W92 nearby a hydroxyl belonging to the 6-phenyl substituent of the substrate coelenterazine. Propagation of this change through a conjugated bond system in the excited state of the product coelenteramide affects the coupling of the N1-position and the hydrogen-bonded Y138. |
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