Regulation Of Inducible Potassium Transporter KdpFABC By The KdpD/KdpE Two-component System In Mycobacterium Smegmatis

Potassium?K⁺?is among the most essential ions required by bacteria to accomplish various cellular processes.Kdp-ATPase is an inducible high affinity potassium uptake system that is widely distributed in bacteria,and is generally regulated by the KdpD/KdpE two-component system.In this study,conducted on Mycobacterium smegmatis,the kdpFABC?encoding Kdp-ATPase?expression was found to be induced by low concentration of K⁺,high concentrations of Na⁺,and/or NH₄⁺ of the medium.While,high concentrations of sucrose,K⁺ and different pH values have minor/no affect on kdpFABC expression.The KdpE was found to be a transcriptional regulator that bound to a specific 22-bp sequence in the promoter region of kdpFABC operon to positively regulate kdpFABC expression.The KdpE binding motif was found to be highly conserved in the promoters of kdpFABC among the mycobacterial species.5'-RACE data indicated a transcriptional start site of the kdp FABC operon within the coding sequence of MSMEG₅391,which comprised a 120-bp long 5'-UTR and an open reading frame of the 87-bp kdpF gene.Moreover,the kdp E deletion resulted in the altered growth rate under normal and low K⁺ conditions.Furthermore,a single transcript?kdp FABCDE?spanning kdpFABC and kdpDE operons was observed under K⁺ limiting conditions.This study provided the first insight into the regulation of kdp FABC operon by the KdpD/KdpE twocomponent system in M.smegmatis.