The Antibiotic Rifamycin Is Selectively Toxic in Blocking Protein Synthesis

Multiple Choice

The antibiotic rifamycin is selectively toxic in blocking protein synthesis in Mycobacterium tuberculosis because

A) the drug binds to the initiator tRNA, preventing the formation of the protein synthesis initiation complex in the bacterial cell.
B) it binds preferentially to bacterial RNA polymerase rather than the eukaryotic protein, effectively halting transcription in the pathogen but not the host.
C) the antibiotic binds to the mRNA once synthesized, preventing it from participating in the initiation complex with the ribosome.
D) bacterial ribosomes are 70s whereas host ribosome are 80s, thus the antibiotic binds to the M.tuberculosis ribosome but does not bind to the eukaryotic machinery.