Abstract
In Synechocystis sp. PCC 6803, a histidine kinase, SphS, induces expression of alkaline phosphates (AP) under phosphate deficiency. Since an amino terminal region of histidine kinase generally contributes to perceive the signal, we characterized function of a hydrophobic region and a PAS domain existing at the amino terminal region of SphS.
We expressed genetically modified SphSs in Synechocystis cells and abilities of the signal sensing were monitored by measuring the alkaline phosphatase (AP) activity. Deletion and point-mutation of PAS domain constitutively expressed AP activity, whilst deletion of the hydrophobic region lost expression of AP activity. Interestingly, substitution of the hydrophobic region with a membrane-bound sequence from another histidine kinase, NrsS, maintained the ability to respond to phosphate availability. These results suggested that the PAS domain of SphS is essential to regulate kinase activity. However, the hydrophobic region is not involved in the signal perception.
