Characterization of two-component system TcrXY in Mycobacterium avium subsp.paratuberculosis

Bacteria survive in environments that experience continuous fluctuation in both physical and chemical aspects by adapting to these changes using sensory-response mechanisms such as Two-Component Systems (TCS). These systems involve autophosphorylation of histidine protein kinase receptors on sensing certain stimuli and activation of cytoplasmic response regulators, usually transcriptional regulators. Mycobacterium avium subspecies paratuberculosis (MAP), the etiological agent involved in Johne's disease, has ten putative TCS, one orphan histidine protein kinase, and five orphan response regulators. Using in vitro beta-galactosidase assays, the MAP tcrXY promoter was found to be induced at pH 4.5, with detergent having an additive effect on induction. MAP recombinant TcrX changed conformation when phosphorylated in vitro. Interestingly, non-phosphorylated TcrX binds to its own promoter, suggesting that TcrXY is autoregulated.