Two-component signal transduction in Synechocystis sp. PCC 6803 under phosphate limitation: role of acetyl phosphate.
The two-component signal transduction, which typically consists of a histidine kinase and a response regulator, is used by bacterial cells to sense changes in their environment. Previously, the SphS-SphR histidine kinase and response regulator pair of phosphate sensing signal transduction has been identified in Synechocystis sp. PCC 6803. In addition, some response regulators in bacteria have been shown to be cross regulated by low molecular weight phosphorylated compounds in the absence of the cognate histidine kinase. The ability of an endogenous acetyl phosphate to phosphorylate the response regulator, SphR in the absence of the cognate histidine kinase, SphS was therefore tested in Synechocystis sp. PCC 6803. The mutant lacking functional SphS and acetate kinase showed no detectable alkaline phosphatase activity under phosphate-limiting growth conditions. The results suggested that the endogenous acetyl phosphate accumulated inside the mutants could not activate the SphR via phosphorylation. On the other hand, exogenous acetyl phosphate could allow the mutant lacking functional acetate kinase and phosphotransacetylase to grow under phosphate-limiting conditions suggesting the role of acetyl phosphate as an energy source. Reverse transcription PCR demonstrated that the transcripts of acetate kinase and phosphotransacetylase genes in Synechocystis sp. PCC 6803 is upregulated in response to phosphate limitation suggesting the importance of these two enzymes for energy metabolism in Synechocystis cells.
Juntarajumnong
Waraporn
W
Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
Eaton-Rye
Julian J
JJ
Incharoensakdi
Aran
A
D000084:Acetate Kinase / Q000235:genetics / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D000071677:Histidine Kinase; D009154:Mutation; D010755:Organophosphates / Q000378:metabolism / Q000494:pharmacology; D010709:Phosphate Acetyltransferase / Q000235:genetics / Q000378:metabolism; D010710:Phosphates / Q000172:deficiency / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D046939:Synechocystis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D010755:Organophosphates; D010710:Phosphates; C011632:acetyl phosphate; D010709:Phosphate Acetyltransferase; D011494:Protein Kinases; D000071677:Histidine Kinase; D000084:Acetate Kinase; D000469:Alkaline Phosphatase