Member of the two-component regulatory system MtrA/MtrB. Binds direct repeat motifs of sequence 5'-GTCACAGCG-3', phosphorylation confers higher affinity. Overexpression decreases bacteria viability upon infection of human THP-1 macrophage cell line, due at least in part to impaired blockage of phagosome-lysosome fusion (upon infection bacteria usually remain in phagosomes). Infecting C57BL/6 mice with an overexpressing strain leads to an attentuated infection in both spleen and lungs. The level of dnaA mRNA increases dramatically. Binds the promoter of dnaA, fbpD, ripA and itself, as well as oriC, which it may regulate. Upon co-overexpression of MrtA and MtrB growth in macrophages is partially restored, dnaA expression is not induced, although mouse infections are still attenuated, suggesting that bacterial growth in macrophages requires an optimal ratio of MtrB to MtrA. Divalent cation. Ca(2+) and Mg(2+) have both been seen in crystal structures. Optimal DNA-binding requires Ca(2+). Probably a monomer when inactive, phosphorylation may permit it to oligomerize. It can oligomerize, and interacts with MrtB (PubMed:20702407, PubMed:21295603). Co-immunoprecipitates with DarG in the presence and absence of darT (PubMed:32634279). Expressed in culture (at protein level). Constitutively expressed in infected human blood-derived macrophages and mouse macrophage cell line J774A. Autoregulates its own expression. C-terminal domain binds DNA and interacts with MtrB. Phosphorylated by MtrB (Probable). Autophosphorylates very slowly. Phosphorylated protein binds DNA better than unphosphorylated. Pupylated at Lys-207 by the prokaryotic ubiquitin-like protein Pup, which leads to its degradation by the proteasome. Essential, it cannot be disrupted. Was identified as a natural substrate of the M.tuberculosis proteasome. Truncated N-terminus.