title: In vivo effects on photosynthesis gene expression of base pair exchanges in the gene encoding the light-responsive BLUF domain of AppA in Rhodobacter sphaeroides.
abstract: The Rhodobacter sphaeroides protein AppA has the unique quality of sensing and transmitting light and redox signals. By acting as antirepressor to the PpsR protein, it acts as a major regulator in photosynthesis gene expression. In this study, we show that by introducing amino acid exchanges into the AppA protein, the in vivo activity as an antirepressor can be greatly altered. The tryptophan 104 to phenylalanine (W104F) base exchange greatly diminished blue-light sensitivity of the BLUF domain. From the obtained in vivo data, the difference in thermal recovery rate of the signaling state of the BLUF domain between the wild type and mutated protein was calculated, predicting an about 10-fold faster recovery in the mutant, which is consistent with in vitro data. Introduction of a tyrosine 21 to phenylalanine (Y21F) or to cysteine (Y21C) mutation led to a complete loss of AppA antirepressor activity, while additionally leading to an increase of photosynthesis gene expression after illumination with high blue-light quantities. Interestingly, this effect is not visible in a W104F/Y21F double mutant that again shows a wild-type-like behavior of the BLUF domain after blue-light illumination, thus restoring the activity of AppA.
authors.affiliation: Institut für Mikro- und Molekularbiologie, University of Giessen, Giessen, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Metz
authors.forename: Johnny
authors.initials: J
authors.lastname: Hendriks
authors.forename: Andreas
authors.initials: A
authors.lastname: Jäger
authors.forename: Klaas
authors.initials: K
authors.lastname: Hellingwerf
authors.forename: Gabriele
authors.initials: G
authors.lastname: Klug
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D020029:Base Pairing; D004926:Escherichia coli / Q000235:genetics / Q000528:radiation effects; D005182:Flavin-Adenine Dinucleotide / Q000235:genetics*; D005420:Flavoproteins / Q000235:genetics*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics* / Q000528:radiation effects; D008027:Light; D008958:Models, Molecular; D009154:Mutation; D010788:Photosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012242:Rhodobacter sphaeroides / Q000235:genetics* / Q000528:radiation effects
chemical_list: C116785:AppA protein, Rhodobacter sphaeroides; D001426:Bacterial Proteins; D005420:Flavoproteins; D005182:Flavin-Adenine Dinucleotide