Participates in transcription elongation, termination and antitermination. Regulated by autoinhibition via interaction of the N-terminal and the C-terminal domains. Autoinhibition may prevent NusG from interacting prematurely with other components of the transcription complex or non-specific interactions with other cellular components. The N-terminal domain interacts with RNAP and the C-terminal domain binds either to Rho or to RpsJ (NusE). Contains an additional, species-specific domain inserted into the N-terminal domain. The N-terminal and C-terminal domains can interact and form a closed conformation. Belongs to the NusG family.