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). Phosphorylated and dephosphorylated by MprB. Truncated N-terminus.