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Redox modulation of flavin and tyrosine determines photoinduced proton-coupled electron transfer and photoactivation of BLUF photoreceptors.
Redox modulation of flavin and tyrosine determines photoinduced proton-coupled electron transfer and photoactivation of BLUF photoreceptors.
- Source :
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The Journal of biological chemistry [J Biol Chem] 2012 Sep 14; Vol. 287 (38), pp. 31725-38. Date of Electronic Publication: 2012 Jul 25. - Publication Year :
- 2012
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Abstract
- Photoinduced electron transfer in biological systems, especially in proteins, is a highly intriguing matter. Its mechanistic details cannot be addressed by structural data obtained by crystallography alone because this provides only static information on a given redox system. In combination with transient spectroscopy and site-directed manipulation of the protein, however, a dynamic molecular picture of the ET process may be obtained. In BLUF (blue light sensors using FAD) photoreceptors, proton-coupled electron transfer between a tyrosine and the flavin cofactor is the key reaction to switch from a dark-adapted to a light-adapted state, which corresponds to the biological signaling state. Particularly puzzling is the fact that, although the various naturally occurring BLUF domains show little difference in the amino acid composition of the flavin binding pocket, the reaction rates of the forward reaction differ quite largely from a few ps up to several hundred ps. In this study, we modified the redox potential of the flavin/tyrosine redox pair by site-directed mutagenesis close to the flavin C2 carbonyl and fluorination of the tyrosine, respectively. We provide information on how changes in the redox potential of either reaction partner significantly influence photoinduced proton-coupled electron transfer. The altered redox potentials allowed us furthermore to experimentally describe an excited state charge transfer intermediately prior to electron transfer in the BLUF photocycle. Additionally, we show that the electron transfer rate directly correlates with the quantum yield of signaling state formation.
- Subjects :
- Amino Acid Sequence
Crystallography, X-Ray methods
Electron Transport
Escherichia coli metabolism
Kinetics
Light
Molecular Conformation
Molecular Sequence Data
Mutagenesis, Site-Directed
Mutation
Oligonucleotides genetics
Spectrophotometry methods
Synechocystis metabolism
Flavins chemistry
Oxidation-Reduction
Photochemistry methods
Photoreceptors, Microbial chemistry
Tyrosine chemistry
Subjects
Details
- Language :
- English
- ISSN :
- 1083-351X
- Volume :
- 287
- Issue :
- 38
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 22833672
- Full Text :
- https://doi.org/10.1074/jbc.M112.391896