Final answer:
In Rho-dependent termination, the rho protein, which is an ATP-dependent helicase, uses energy from ATP hydrolysis to unwind the RNA-DNA hybrid and facilitate the termination of transcription.
Step-by-step explanation:
The energy requiring activity in Rho-dependent termination of transcription is the action of the rho protein, which is an ATP-dependent helicase. During transcription in prokaryotes, when RNA polymerase encounters a rho utilization (rut) site on the nascent RNA, the rho protein binds to this site. Rho then moves towards the 3' end of the RNA, using the energy from ATP hydrolysis to unwind the RNA-DNA hybrid and break the hydrogen bonds, effectively separating the newly synthesized RNA strand from the DNA template, and terminating transcription.