A three-component signalling system fine-tunes expression kinetics of HPPK responsible for folate synthesis by positive feedback loop during stress response of Xanthomonas campestris.

摘要: During adaptation to environments, bacteria employ two-component signal transduction systems, which contain histidine kinases and response regulators, sense respond exogenous cellular stimuli in an accurate spatio-temporal manner. Although the protein phosphorylation process between kinase regulator has been well documented, molecular mechanism fine-tuning levels of regulators is comparatively less studied. Here we combined genetic biochemical approaches reveal that a hybrid kinase, SreS, involved SreK-SreR phosphotransfer control salt stress bacterium Xanthomonas campestris. The N-terminal receiver domain SreS acts as phosphate sink by competing with SreR accept phosphoryl group from latter's cognate SreK. This regulatory critical for bacterial survival because dephosphorylated participates activating one tandem promoters (P2) at 5' end sreK-sreR-sreS-hppK operon, then modulates transcriptional surge stress-responsive gene hppK, required folic acid synthesis. Therefore, our study dissects positive feedback loop 'three-component' signalling system fine-tunes expression kinetics downstream genes.