A cryptochrome-like protein is involved in the regulation of photosynthesis genes in Rhodobacter sphaeroides.
Blue light receptors belonging to the cryptochrome/photolyase family are found in all kingdoms of life. The functions of photolyases in repair of UV-damaged DNA as well as of cryptochromes in the light-dependent regulation of photomorphogenetic processes and in the circadian clock in plants and animals are well analysed. In prokaryotes, the only role of members of this protein family that could be demonstrated is DNA repair. Recently, we identified a gene for a cryptochrome-like protein (CryB) in the alpha-proteobacterium Rhodobacter sphaeroides. The protein lacks the typical C-terminal extension of cryptochromes, and is not related to the Cry DASH family. Here we demonstrate that CryB binds flavin adenine dinucleotide that can be photoreduced by blue light. CryB binds single-stranded DNA with very high affinity (K(d) approximately 10(-8) M) but double-stranded DNA and single-stranded RNA with far lower affinity (K(d) approximately 10(-6) M). Despite of that, no in vitro repair activity for pyrimidine dimers in single-stranded DNA could be detected. However, we show that CryB clearly affects the expression of genes for pigment-binding proteins and consequently the amount of photosynthetic complexes in R. sphaeroides. Thus, for the first time a role of a bacterial cryptochrome in gene regulation together with a biological function is demonstrated.
Hendrischk
Anne-Kathrin
AK
Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany.
Frühwirth
Sebastian Walter
SW
Moldt
Julia
J
Pokorny
Richard
R
Metz
Sebastian
S
Kaiser
Gebhard
G
Jäger
Andreas
A
Batschauer
Alfred
A
Klug
Gabriele
G
D001426:Bacterial Proteins / Q000378:metabolism*; D003067:Coenzymes / Q000378:metabolism; D056931:Cryptochromes / Q000378:metabolism*; D004260:DNA Repair; D004269:DNA, Bacterial / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D007700:Kinetics; D008027:Light; D010084:Oxidation-Reduction; D010788:Photosynthesis; D011485:Protein Binding; D011740:Pyrimidine Dimers / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000502:physiology*
D001426:Bacterial Proteins; D003067:Coenzymes; D056931:Cryptochromes; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D011740:Pyrimidine Dimers; D005182:Flavin-Adenine Dinucleotide