A blue light inducible two-component signal transduction system in the plant pathogen Pseudomonas syringae pv. tomato.
The open reading frame PSPTO2896 from the plant pathogen Pseudomonas syringae pv. tomato encodes a protein of 534 amino acids showing all salient features of a blue light-driven two-component system. The N-terminal LOV (light, oxygen, voltage) domain, potentially binding a flavin chromophore, is followed by a histidine kinase (HK) motif and a response regulator (RR). The full-length protein (PST-LOV) and, separately, the RR and the LOV+HK part (PST-LOV(DeltaRR)) were heterologously expressed and functionally characterized. The two LOV proteins showed typical LOV-like spectra and photochemical reactions, with the blue light-driven, reversible formation of a covalent flavin-cysteine bond. The fluorescence changes in the lit state of full-length PST-LOV, but not in PST-LOV(DeltaRR), indicating a direct interaction between the LOV core and the RR module. Experiments performed with radioactive ATP uncover the light-driven kinase activity. For both PST-LOV and PST-LOV(DeltaRR), much more radioactivity is incorporated when the protein is in the lit state. Furthermore, addition of the RR domain to the fully phosphorylated PST-LOV(DeltaRR) leads to a very fast transfer of radioactivity, indicating a highly efficient HK activity and a tight interaction between PST-LOV(DeltaRR) and RR, possibly facilitated by the LOV core itself.
Cao
Z
Z
Max-Planck-Institut für Bioanorganische Chemie, D-45470 Mülheim, Germany.
Buttani
V
V
Losi
A
A
Gärtner
W
W
D001426:Bacterial Proteins / Q000502:physiology* / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D008027:Light; D018551:Solanum lycopersicum / Q000382:microbiology*; D044224:Pseudomonas syringae / Q000502:physiology* / Q000528:radiation effects*; D011829:Radiation Dosage
D001426:Bacterial Proteins