The extended N-terminal region of SphS is required for detection of external phosphate levels in Synechocystis sp. PCC 6803.
A novel 47 amino acid extension at the N-terminus of the SphS histidine kinase has been identified in the cyanobacterium Synechocystis sp. PCC 6803. Here, we demonstrate this region is required for activation of the SphS-SphR phosphate-sensing two-component system under phosphate-limiting conditions and mutants lacking this extension do not show constitutive alkaline phosphatase activity when the negative regulator SphU is inactivated. We have also identified a putative membrane-associated domain within this region involved in control of the Pho regulon. In addition, there are two high-affinity ABC-type phosphate uptake systems in this organism. Our results demonstrate that the Pst1 system, but not the Pst2 system, is required for suppression of the Pho regulon under phosphate-sufficient conditions. Deletion of the pst1 operon and disruption of the membrane-spanning domain may both target the same control mechanism since constitutive alkaline phosphatase activity is similar in the double and single mutants.
Burut-Archanai
Surachet
S
Department of Biochemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand.
Incharoensakdi
Aran
A
Eaton-Rye
Julian J
JJ
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001692:Biological Transport; D008969:Molecular Sequence Data; D010710:Phosphates / Q000378:metabolism*; D010770:Phosphotransferases / Q000235:genetics / Q000502:physiology*; D017434:Protein Structure, Tertiary; D018085:Regulon; D017384:Sequence Deletion; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*
D001426:Bacterial Proteins; D010710:Phosphates; D014157:Transcription Factors; D010770:Phosphotransferases; C081252:SphS protein, Synechococcus sp.