Surachet Burut-ArchanaiAran IncharoensakdiJulian J. Eaton-RyeUniversity of OtagoMahidol University2018-09-132018-09-132009-01-16Biochemical and Biophysical Research Communications. Vol.378, No.3 (2009), 383-388109021040006291X2-s2.0-57749193964https://repository.li.mahidol.ac.th/handle/123456789/27297A 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. © 2008 Elsevier Inc. All rights reserved.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyArticleSCOPUS10.1016/j.bbrc.2008.11.012