Protein structure, spectral properties, and photobiological function of lumazine protein

John W. Lee; Elizabeth A. Bradley; Dennis J. O'Kane

doi:10.1117/12.58209

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1 April 1992 Protein structure, spectral properties, and photobiological function of lumazine protein

John W. Lee; Elizabeth A. Bradley; Dennis J. O'Kane

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Proceedings Volume 1640, Time-Resolved Laser Spectroscopy in Biochemistry III; (1992) https://doi.org/10.1117/12.58209
Event: OE/LASE '92, 1992, Los Angeles, CA, United States

Abstract

Protein sequence analysis, nuclear magnetic resonance, and fluorescence dynamics have been applied in a determination of the interactions of the lumazine derivative with the amino acid residues in the proposed ligand binding site of lumazine protein. It is these interactions that `tune' the excited state properties of the bound lumazine so that it can perform its photobiological function as the emitter of bioluminescence in Photobacterium species. A three- way sequence alignment shows that lumazine protein is homologous with the yellow- fluorescent protein of Vibrio fischeri and the riboflavin synthase from Bacillus subtilis. This last enzyme is ubiquitous in procaryotes, and utilizes two of these same lumazines as substrates for the production of riboflavin. By analogy with riboflavin synthase, a short sequence in the lumazine protein has been suggested as the ligand binding site. In riboflavin synthase there is a second binding site, but this is absent in lumazine protein, thus negating any synthase activity for this protein. Hydrogen bonds to the residues in this binding domain and `freeze' the lumazine structure into the highly polar tautomer deduced from NMR evidence. This also accounts for the rigidity of binding shown by the 23 ns (2 degree(s)C) rotational correlation time of the bound ligand as well as the strong blue shift of the fluorescence maximum, from 490 nm free to 475 nm when bound.

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John W. Lee, Elizabeth A. Bradley, and Dennis J. O'Kane "Protein structure, spectral properties, and photobiological function of lumazine protein", Proc. SPIE 1640, Time-Resolved Laser Spectroscopy in Biochemistry III, (1 April 1992); https://doi.org/10.1117/12.58209

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