Prokaryotic promoter elements: What is the usual consensus sequence of the Pribnow box (−10 element) in bacterial promoters?

Introduction / Context:Promoters are DNA sequences that position RNA polymerase for accurate initiation of transcription. In bacteria, two key hexamer elements are commonly recognized: the −35 region and the −10 region, also known as the Pribnow box.

Given Data / Assumptions:

• The Pribnow box lies approximately 10 base pairs upstream of the transcription start site.
• Consensus sequences reflect the most common nucleotides at each position among strong promoters.
• We are dealing with DNA sequences written in the coding strand sense.

Concept / Approach:The canonical −10 element consensus is TATAAT. This AT-rich sequence facilitates DNA unwinding during open complex formation by RNA polymerase. The −35 element has a different consensus, typically TTGACA, and provides an additional binding site for sigma factor within the holoenzyme.

Step-by-Step Solution: Recall that the −10 (Pribnow) consensus is AT-rich. Match options with known consensus: TATAAT fits the −10 box. Recognize TTGACA as the −35 element, not the −10 element. Select TATAAT as the correct answer.

Verification / Alternative check:Mutational analyses show that deviations from TATAAT at key positions reduce promoter strength, confirming the functional importance of this consensus.

Why Other Options Are Wrong:

• TTGACA: −35 consensus, not −10.
• AUAUA / UUUUU: RNA-like sequences, not DNA promoter elements.
• CGCGCG: GC-rich and does not serve as a standard −10 element.

Common Pitfalls:Confusing RNA sequences with DNA promoter consensus or mixing up the −35 and −10 elements.

Final Answer:TATAAT.