Protein structure and bioluminescent spectra for firefly bioluminescence

Modern theory on general and specific effects of microenvironment on emission spectra was used for explanation of spectral differences for both natural and mutant forms of beetle luciferases, as well as for bioluminescence emitter oxyluciferin in model systems. For the analysis, both authors' and other published data were used. It was shown that active site mutations that resulted in spectral shifts of bioluminescence as a rule caused substantial decrease in the catalytic activity of the enzyme. At the same time, mutations in the conservative regions of the protein amino acid sequence that were in the periphery of the protein globe resulted in red shift of the bioluminescence spectra without affecting catalytic activity. Correlation was observed between the value of spectral shift and polarizability of the introduced amino acid residue: the higher the polarizability, the larger was the red shift of bioluminescence.