Which region of sigma 70 is recognized by discriminators?

The region of sigma 70 that is recognized by discriminators is indeed 1.2. This region plays a critical role in promoter recognition during the initiation of transcription in prokaryotes. Specifically, the 1.2 region interacts with the discriminator region of the promoter, which is a sequence found just upstream of the transcription start site.

Discriminators are sequences that help in determining whether sigma 70 can bind effectively to a particular promoter. The interaction between the 1.2 region of sigma 70 and these discriminators helps the RNA polymerase holoenzyme to differentiate between strong and weak promoters, ensuring that transcription is initiated correctly.

Furthermore, this specificity is essential because it enhances the affinity of RNA polymerase for certain promoters, dictating the transcriptional machinery's efficiency and fidelity in recognizing the appropriate genes for expression under various cellular conditions.