Spectroscopic comparison of FMN in LOV protein YtvA-C62S and in AOT-reversed micelles

L. VALLE; C. D. BORSARELLI; A. LOSI; W. GÄRTNER

Córdoba

Encuentro; XI ENCUENTRO LATINOAMERICANO DE FOTOQUIMICA Y FOTOBIOLOGIA; 2012

Universidad Nacional de Río Cuarto

The flavin mononucleotide (FMN) containing protein YtvA from Bacillus subtillis was described as the first prokaryotic phototropin-like blue-light-responsive photoreceptor [1], which upon light excitation, the excited triplet state decays in the s time-range to form a photoadduct through a covalent bond –C-S– by reaction with the conserved cystein residue Cys62 initiating the transduction of the light stimulus. The replacement of Cys62 by serine (Ser) produces the YtvA-C62S mutant that does not show formation of photoadduct. However, both native and mutant proteins exhibit similar UV-Vis, excitation anisotropy, and fluorescence spectra, but are dissimilar with those for FMN in buffer solutions, indicating the effect of both environmental and motional constrains imposed by the active site of the protein. Interestingly, some of these photophysical properties of FMN in the protein were similar to those observed in sodium docusate (AOT) reverse micelles at low water content (w0, [water]/[AOT] < 3) [2]. The results are discussed as a function of the hydrogen-bonding nature of the isoalloxazine ring of FMN in both environments.