Two dimers 

Tetramers

Protofilaments (Tetramers are assembled end to end)

Protofibril (Four protofilaments)

10-nm filament (Four protofibrils associate side

#Id: 2435

#Unit 3. Fundamental Processes

Rho is a member of the family of hexameric ATP-dependent helicases. Each subunit has an RNA-binding domain and an ATP hydrolysis domain. 

#Id: 2436

#Unit 3. Fundamental Processes

Rho has an N-terminal, RNA-binding domain and a C-terminal ATPase domain. A hexamer in the form of a gapped ring binds RNA along the exterior of the N-terminal domains. The 5’ end of the RNA is bound by a secondary binding site in the interior of the hexamer.

#Id: 2437

#Unit 3. Fundamental Processes

The initial form of rho is a gapped ring, but binding of the RNA converts it to a closed ring.

#Id: 2438

#Unit 3. Fundamental Processes

Rho needs to translocate along RNA from the rut site to the actual point of termination.

#Id: 2439

#Unit 3. Fundamental Processes

The coupling between transcription and translation has important consequences for rho action. Rho must first have access to RNA upstream of the transcription complex and then moves along the RNA to catch up with RNA polymerase. 

#Id: 2440

#Unit 3. Fundamental Processes

In some cases, a nonsense mutation in one gene of a transcription unit was found to prevent the expression of subsequent genes in the unit even though both genes had their own ribosome binding sites, an effect called polarity.