[1] Rho factor binds to the transcription terminator pause site, an exposed region of single stranded RNA (a stretch of 72 nucleotides) after the open reading frame at C-rich/G-poor sequences that lack obvious secondary structure.

Rho is a member of the RecA/SF5 family of ATP-dependent hexameric helicases that function by wrapping nucleic acids around a single cleft extending around the entire hexamer.

Rho's key function is its helicase activity, for which energy is provided by an RNA-dependent ATP hydrolysis.

The initial binding site for Rho is an extended (~70 nucleotides, sometimes 80–100 nucleotides) single-stranded region, rich in cytosine and poor in guanine, called the rho utilisation site (rut), in the RNA being synthesised, upstream of the actual terminator sequence.

As a result, the enzyme is released, and the distal regions of the transcription unit are never transcribed.