Chapter 16 - Regulation of Gene Expression - 16.1 - Prokaryotic Gene Expression Is Regulated in Operons - 16.1 Recap - Learning Outcomes - Page 341: 4

Though not all promoters are identical, they do share consensus sequences which allows them to be identified by the RNA polymerase and other proteins. Sigma factors refer to prokaryotic proteins that attach to RNA polymerase, directing it to a specific groups of promoters. The RNA polymerase has to bind to a sigma factor before it can recognize a promoter and initiate transcription.

Though not all promoters are identical, they do share consensus sequences which allows them to be identified by the RNA polymerase and other proteins. Sigma factors refer to prokaryotic proteins that attach to RNA polymerase, directing it to a specific groups of promoters. The RNA polymerase has to bind to a sigma factor before it can recognize a promoter and initiate transcription.