Member of the two-component regulatory system MprB/MprA which contributes to maintaining a balance among several systems involved in stress resistance and is required for establishment and maintenance of persistent infection in the host. In response to environmental signals MprB acts as both a membrane-associated protein kinase that undergoes autophosphorylation and subsequently transfers the phosphate to MprA, and a protein phosphatase that dephosphorylates phospho-MprA. MprB/MprA is involved in regulation of numerous stress-responsive genes, including up-regulation of two sigma factors, sigE and sigB as well as pepD and mprA, and repression of multiple genes from regulons associated with hypoxia, starvation and iron metabolism. The majority of genes regulated by MprB/MprA under a particular stress condition are different from those induced during normal growth, but several genes are commonly regulated under more than one condition. ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Induced by MprA. Differentially up-regulated under different stress conditions, such as low concentrations of detergents and alkaline pH. Induced by low concentrations of sodium dodecyl sulfate (SDS) in a SigE-dependent manner. In strain ATCC 25618 / H37Rv, repressed during growth in macrophages. Highly up-regulated during the early stages of invasion of the human blood-brain barrier. Autophosphorylated. Deletion experiments show that amino acids 95-133 are required for activation of MprA. Was identified as a high-confidence drug target.