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1 September 2003 Initial Characterization of the Primary Photochemistry of AppA, a Blue-light–using Flavin Adenine Dinucleotide–domain Containing Transcriptional Antirepressor Protein from Rhodobacter sphaeroides: A Key Role for Reversible Intramolecular Proton Transfer from the Flavin Adenine Dinucleotide Chromophore to a Conserved Tyrosine?
Wouter Laan, Michael A. van der Horst, Ivo H. van Stokkum, Klaas J. Hellingwerf
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Abstract

The flavin adenine dinucleotide (FAD)–containing photoreceptor protein AppA (in which the FAD is bound to a novel so-called BLUF domain) from the purple nonsulfur bacterium Rhodobacter sphaeroides was previously shown to be photoactive by the formation of a slightly redshifted long-lived intermediate that is thought to be the signaling state. In this study, we provide further characterization of the primary photochemistry of this photoreceptor protein using UV–Vis and Fourier-transform infrared spectroscopy, pH measurements and site-directed mutagenesis. Available evidence indicates that the FAD chromophore of AppA may be protonated in the receptor state, and that it becomes exposed to solvent in the signaling state. Furthermore, experimental data lead to the suggestion that intramolecular proton transfer (that may involve [anionic] Tyr-17) forms the basis for the stabilization of the signaling state.

Wouter Laan, Michael A. van der Horst, Ivo H. van Stokkum, and Klaas J. Hellingwerf "Initial Characterization of the Primary Photochemistry of AppA, a Blue-light–using Flavin Adenine Dinucleotide–domain Containing Transcriptional Antirepressor Protein from Rhodobacter sphaeroides: A Key Role for Reversible Intramolecular Proton Transfer from the Flavin Adenine Dinucleotide Chromophore to a Conserved Tyrosine?," Photochemistry and Photobiology 78(3), 290-297, (1 September 2003). https://doi.org/10.1562/0031-8655(2003)078<0290:ICOTPP>2.0.CO;2
Received: 27 March 2003; Accepted: 1 June 2003; Published: 1 September 2003
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