title: Interaction of two photoreceptors in the regulation of bacterial photosynthesis genes.
abstract: The expression of photosynthesis genes in the facultatively photosynthetic bacterium Rhodobacter sphaeroides is controlled by the oxygen tension and by light quantity. Two photoreceptor proteins, AppA and CryB, have been identified in the past, which are involved in this regulation. AppA senses light by its N-terminal BLUF domain, its C-terminal part binds heme and is redox-responsive. Through its interaction to the transcriptional repressor PpsR the AppA photoreceptor controls expression of photosynthesis genes. The cryptochrome-like protein CryB was shown to affect regulation of photosynthesis genes, but the underlying signal chain remained unknown. Here we show that CryB interacts with the C-terminal domain of AppA and modulates the binding of AppA to the transcriptional repressor PpsR in a light-dependent manner. Consequently, binding of the transcription factor PpsR to its DNA target is affected by CryB. In agreement with this, all genes of the PpsR regulon showed altered expression levels in a CryB deletion strain after blue-light illumination. These results elucidate for the first time how a bacterial cryptochrome affects gene expression.
authors.affiliation: Institut für Mikrobiologie und Molekularbiologie, Universität Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Metz
authors.forename: Kerstin
authors.initials: K
authors.lastname: Haberzettl
authors.forename: Sebastian
authors.initials: S
authors.lastname: Frühwirth
authors.forename: Kristin
authors.initials: K
authors.lastname: Teich
authors.forename: Christian
authors.initials: C
authors.lastname: Hasewinkel
authors.forename: Gabriele
authors.initials: G
authors.lastname: Klug
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D005420:Flavoproteins / Q000737:chemistry / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008027:Light; D020283:Photoreceptors, Microbial / Q000737:chemistry / Q000378:metabolism*; D010788:Photosynthesis / Q000235:genetics*; D054730:Protein Interaction Domains and Motifs; D018085:Regulon; D012097:Repressor Proteins / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000235:genetics*; D020798:Two-Hybrid System Techniques; D015003:Yeasts / Q000235:genetics / Q000528:radiation effects
chemical_list: C116785:AppA protein, Rhodobacter sphaeroides; D001426:Bacterial Proteins; D005420:Flavoproteins; D020283:Photoreceptors, Microbial; D012097:Repressor Proteins