Two-component regulator MtrA interacts with the regulatory region of dnaA. (A) The regulatory sequence of the dnaA initiator gene was cloned into the reporter genes upstream of HIS3-aadA of the reporter vector pBXcmT (24). (B) The interaction between MtrA and the promoter region of dnaA was measured by bacterial one-hybrid analysis. Upper panel: bacterial two-hybrid plates. Lower panel: an outline of the plates in the upper panel. Each unit represents the corresponding co-transformant in the plates. CK+: co-transformant containing pBX-Rv2031p and pTRG-Rv3133c as a positive control (24). CK-: co-transformant containing pBX-Rv2031p and pTRG-Rv3133c-deltaC as a negative control (24). SsoDNA, an unrelated archaeal DNA sequence, was also used a negative control. (C) SPR assays for the binding of dnaA promoter chip by MtrA. (D) The specific interaction between the regulatory region of the M. tuberculosis dnaA gene was assayed by SPR. Unlabeled promoter DNA was used as competition for the binding of MtrA with DNA on chip. An overlay plot was produced to show the interactions.