Responds to a phosphorelay sensor to initiate a change in cell state or activity. The activity of the response regulator is regulated by transfer of a phosphate from a histidine residue in the sensor, to an aspartate residue in the response regulator. Many but not all response regulators act as transcriptional regulators to elicit a response.

Interacting selectively and non-covalently with a sequence of DNA that is an enhancer region that helps activate transcription of a gene or operon by a bacterial-type RNA polymerase. Enhancers for sigma-54 holoenzymes are typically located 80 to 150 base pairs upstream from the transcription start site, although they can be further away or may be downstream of the promoter. Some transcription units dependent on sigma-70 holoenzymes may also include enhancer sequences.

A protein or a member of a complex that interacts selectively and non-covalently with a specific DNA sequence (sometimes referred to as a motif) within the regulatory region of a gene to modulate transcription. Regulatory regions include promoters (proximal and distal) and enhancers. Genes are transcriptional units, and include bacterial operons.