MCQ
The compound rifampicin is very:
- APotent inhibitor of bacterial RNA polymerases
- BPotent inhibitor of bacterial DNA polymerases
- CWeak inhibitor of bacterial RNA polymerases
- DWeak inhibitor of bacterial DNA polymerases
Explanation:
Rifampicin serves as the potent inhibitor of bacterial RNA synthesis by binding to the beta-subunit of bacterial RNA polymerases thereby preventing the promoter clearance step of transcription. The active site of the enzyme is present in the cleft of beta and beta prime subunit.
Transcription initiation includes binding of polymerase to the promoter, forming initiation complex, followed by transcription initiation within the complex. This, in turn, leads to a conformational change to convert the complex to the elongation form that allows movement of the transcription complex away from the promoter. It is called promoter clearance.
Rifampicin does not affect any enzyme of DNA synthesis, making option B and D incorrect. Since the toxin affects the subunit responsible for promoter clearance step which is fundamental for elongation phase of protein synthesis; it is a potent inhibitor.
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