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. Functions as a transcriptional regulator that recognizes a 19-bp nucleotide motif comprizing two loosely conserved 8-bp direct DNA-binding motif repeats separated by a 3-bp spacer region (By similarity). MprB/MprA up-regulates expression of mprA and pepD. Monomer. Interaction with each conserved 8-bp repeat requires tandem binding by two protein monomers (By similarity). Autoregulated. Induced by low concentrations of sodium dodecyl sulfate (SDS). In strain BCG / Pasteur, induced during growth in macrophages. Phosphorylated and dephosphorylated by MprB.