One Protein, Two Chromophores: Comparative Spectroscopic Characterization of 6,7-Dimethyl-8-ribityllumazine and Riboflavin Bound to Lumazine Protein

• DOI: 10.1021/jp507618f
• Publication Date: 2014-10-17T22:40:13Z
• Authors: Bernd Paulus; Boris Illarionov; Daniel Nohr; Guillaume Roellinger; Sylwia Kacprzak; Markus Fischer; Stefan Weber; Adelbert Bacher; Erik Schleicher
• Keywords: Flavoprotein; Chromophore

We investigated the lumazine protein from Photobacterium leiognathi in complex with its biologically active cofactor, 6,7-dimethyl-8-ribityllumazine, at different redox states and compared results samples containing a riboflavin cofactor. Using anaerobic photoreduction, we were able to record optical absorption kinetics both cofactors similar environments. It could be demonstrated that is stabilize neutral ribolumazine radical ∼35% yield. The state was further by W-band continuous-wave EPR X-band pulsed ENDOR spectroscopy. Here, principal values of g-tensor an almost complete mapping proton hyperfine couplings (hfcs) obtained. Remarkably, g-tensor's components are those respective riboflavin-containing protein; however, hfcs show noticeable differences. Comparing time-resolved fluorescence data ribolumazine-containing samples, solely but no signs any intermediate or triplet identified. This contrast for which high yield photogenerated some excited flavin detected using These clearly demonstrate redox-active molecule could, principle, employed as cofactor other enzymatic reactions.