Final answer:
In E. coli, the rho protein is required for rho-dependent transcription termination, releasing the RNA from the transcription bubble when RNA polymerase stalls at a run of G nucleotides.
Step-by-step explanation:
In E. coli, the transcription termination of certain genes requires an RNA-binding protein called the rho protein. This protein is essential for the process known as rho-dependent termination, which is one of two mechanisms bacteria use to signal the end of transcription.
The rho protein operates as an ATP-dependent helicase, moving along the nascent mRNA behind the RNA polymerase. When RNA polymerase transcribes a run of G nucleotides on the DNA template and stalls, the rho protein catches up, breaking the hydrogen bonds between the RNA and the DNA.
This action results in the RNA being released from the transcription bubble, thereby terminating transcription.