Question

Which of the following is not related with termination of transcription in E. coli?

(1). ppGpp
(2). pppGpp
(3). Alarmones
(4). pGp

• A. ppGpp
• B. pppGpp
• C. Alarmones
• D. pGp

Hint:

Note that options 1 (ppGpp), 2 (pppGpp), and 3 (Alarmones) refer to the same biological regulatory system in bacteria.
Isolating the duplicate terms helps identify (4) as the correct choice.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Bacterial transcription regulation involves various signaling nucleotides.
During cellular stress, such as nutrient or amino acid starvation, bacteria initiate the stringent response. This response is coordinated by the synthesis of unusual hyperphosphorylated guanosine nucleotides.

Step 2: Detailed Explanation:
Let us analyze the relationships of the listed options in bacterial transcription:
1. ppGpp and pppGpp (1 and 2): Guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp) are regulatory nucleotides synthesized by enzymes such as RelA and SpoT.
When uncharged tRNAs accumulate in the ribosome, these nucleotides are produced.
2. Alarmones (3): ppGpp and pppGpp are collectively referred to as alarmones.
These signaling molecules bind directly to RNA polymerase, altering its promoter affinity to suppress the transcription of stable RNA genes (rRNAs and tRNAs) and upregulate metabolic genes.
Because they directly regulate transcription initiation, elongation rates, and transcriptional pausing, they are intimately related to the control of transcription in E. coli.
3. pGp (4): The monophosphate-related nucleotide 5'-phosphoadenosine 3'-phosphate or similar pGp forms do not serve as established transcriptional regulators or alarmones in the stringent response of E. coli.
Therefore, pGp is the only term listed that is not functionally related to these transcription regulation systems.

Step 3: Final Answer:
The molecule not related to the system is pGp, which corresponds to option (D).