Raman Spectra of Flavin Bound in Flavodoxins and in Other Flavoproteins. Evidence for Structural Variations in the Flavin-Binding Region

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Abstract
The resonance coherent anti-Stokes Raman scattering (CARS) spectra for a number of flavoproteins are found to be fingerprints for the particular type of flavoprotein. One group studied were the bacterial flavodoxins: Desulfovibrio vulgaris, Desulfovibrio desulfuricans, Azotobacter vinelandii, Megasphaera elsdenii, Clostridium kluyveri and Clostridium formicoaceticum. The other examples were the enzymes lactate monooxygenase (Mycobacterium smegmatis) and glucose oxidase (Aspergillus niger), FMN complexed to Vibrio harveyi luciferase, and a partially characterized non-fluorescent flavoprotein from Photobacterium leiognathi. In the frequency range 1700-1100 cm-1, differences in the frequency positions and relative intensities of the prominent bands are reflections of the interactions of the isoalloxazine ring with the protein. Based on tentative assignment of the vibrational modes in flavin models, the spectra are interpreted in terms of H-bonding between the amino acid residues of the binding site and particular atoms of the isoalloxazine ring.