Abstract
A histidine kinase, Hik33, in Synechocystis sp. PCC 6803 regulates gene expression under various stress conditions. Generally hisitidine kinases perceive specific stimuli via signal-input domains (SID) located at the N-terminal portions. An SID in Hik33 includes two transmembrane helixes, a periplasmic loop, HAMP and PAS domains. To investigate roles of the SID in the perception of signals, we expressed a chimeric kinase combining the SID from Hik33 with a kinase domain from SphS, which regulates expression of the phoA gene for alkaline phosphatase, in the mutant of SphS. And the expression levels of the phoA gene were determined under standard, chilling or salt conditions. The chimeric kinases expressed the phoA gene under the standard conditions and repressed it under the stress conditions. Removals of the regions of SID from the chimeric sensor indicated the important regions for perception of the signals to regulate the gene expression.
