Activator of the Pm promoter, which controls middle genes expression. Activation of Pm allows expression of protein C necessary for late gene expression. In addition to Mor binding, activation of Pm might require the interaction of Mor with the C-terminus of host RNAP subunits RpoA and RpoH. Homodimer. This protein is constitively expressed from the Pgem promoter unlike most other early proteins which are expressed under the control of the Pe promoter. Its expression seems to escape repression by repressor protein c and thus could occur throughout latency (Probable). The dimerization domain in the N-terminus and the DNA-binding domain in the C-terminus are connected by a linker containing a beta-strand. Belongs to the c/mor transcriptional regulatory family.