The photosensor protein Ppr of Rhodocista centenaria is linked to the chemotaxis signalling pathway.
BACKGROUND
Rhodocista centenaria is a phototrophic α-proteobacterium exhibiting a phototactic behaviour visible as colony movement on agar plates directed to red light. As many phototrophic purple bacteria R. centenaria possesses a soluble photoactive yellow protein (Pyp). It exists as a long fusion protein, designated Ppr, consisting of three domains, the Pyp domain, a putative bilin binding domain (Bbd) and a histidine kinase domain (Pph). The Ppr protein is involved in the regulation of polyketide synthesis but it is still unclear, how this is connected to phototaxis and chemotaxis.


RESULTS
To elucidate the possible role of Ppr and Pph in the chemotactic network we studied the interaction with chemotactic proteins in vitro as well as in vivo. Matrix-assisted coelution experiments were performed to study the possible communication of the different putative binding partners. The kinase domain of the Ppr protein was found to interact with the chemotactic linker protein CheW. The formation of this complex was clearly ATP-dependent. Further results indicated that the Pph histidine kinase domain and CheW may form a complex with the chemotactic kinase CheAY suggesting a role of Ppr in the chemotaxis signalling pathway. In addition, when Ppr or Pph were expressed in Escherichia coli, the chemotactic response of the cells was dramatically affected.


CONCLUSIONS
The Ppr protein of Rhodocista centenaria directly interacts with the chemotactic protein CheW. This suggests a role of the Ppr protein in the regulation of the chemotactic response in addition to its role in chalcone synthesis.
Institute of Microbiology and Molecular Biology, University of Hohenheim, Garbenstrasse 30 D-70593 Stuttgart, Germany.
Sven
S
Kreutel
Andreas
A
Kuhn
Dorothee
D
Kiefer
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002633:Chemotaxis; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D020283:Photoreceptors, Microbial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012246:Rhodospirillum / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment; D015398:Signal Transduction
D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; C120281:Ppr protein, Rhodospirillum centenum; C051236:CheW protein, Bacteria