Member of the two-component regulatory system TorS/TorR involved in the anaerobic utilization of trimethylamine-N-oxide (TMAO). Phosphorylated TorR activates the transcription of the torCAD operon by binding to four decameric boxes located in the torCAD promoter. Box1, 2 and 4 contain the DNA sequence 5'-CTGTTCATAT-3' and box3 contains the DNA sequence 5'-CCGTTCATCC-3'. Phosphorylated as well as unphosphorylated TorR negatively regulates its own expression by binding to box1 and 2. Interacts with TorI. TorI binds to the effector domain of TorR. This interaction, which does not interfere with TorR DNA binding activity, probably prevents the recruitment of RNA polymerase to the torCAD promoter. Phosphorylated and dephosphorylated by TorS.