Rifampicin is not a translation inhibitor; it targets bacterial RNA polymerase to block transcription. Chloramphenicol, cycloheximide, and puromycin each halt protein synthesis at ribosome stages, making Rifampicin the correct choice (D) in this CSIR NET-style question.​

Option Analysis

Chloramphenicol binds the peptidyl transferase center (PTC) on the bacterial 50S ribosomal subunit, preventing peptide bond formation during elongation in a context-dependent manner.​
Cycloheximide inhibits eukaryotic translation by blocking eEF2-mediated translocation on the 60S subunit’s E-site.​
Puromycin mimics aminoacyl-tRNA, incorporating into the nascent chain at the PTC to cause premature termination.​
Rifampicin binds the β-subunit of bacterial RNA polymerase, sterically blocking RNA elongation after 2-3 nucleotides, thus inhibiting transcription upstream of translation.​

Translation inhibitors like chloramphenicol, cycloheximide, and puromycin disrupt protein synthesis at the ribosome, crucial for CSIR NET life sciences preparation. Rifampicin stands out as it inhibits transcription, not translation, by targeting RNA polymerase.​

Mechanisms of Action

• Chloramphenicol (Prokaryotic PTC blocker): Inhibits peptidyl transferase on 50S subunit, context-specific via nascent peptide sequences.​

• Cycloheximide (Eukaryotic translocation blocker): Binds 60S E-site, halts eEF2-driven translocation.​

• Puromycin (tRNA mimic): Enters A-site, forms puromycylated chain, terminates prematurely.​

• Rifampicin (Transcription inhibitor): Blocks RNA extension in polymerase DNA/RNA channel.​

Exam Relevance

These distinctions appear in CSIR NET questions on antibiotic targets, with Rifampicin as the non-translation inhibitor. Understanding prokaryotic vs eukaryotic specificity aids in differentiating options.​