Member of the two-component regulatory system PrrB/PrrA that is involved specifically in early intracellular multiplication of Mycobacterium and is essential for its viability. Functions as a sensor protein kinase which is autophosphorylated at a histidine residue and transfers its phosphate group to the conserved aspartic acid residue in the regulatory domain of PrrA. In turn, PrrA binds to the upstream promoter regions of target genes including itself to positively regulate their expression. ATP + protein L-histidine = ADP + protein N-phospho-L-histidine. Autophosphorylated.