How does Streptomycin inhibit protein synthesis?
Streptomycin is bactericidal in action. It inhibits protein synthesis by combining irreversibly with the 30S subunit of the70S ribosomes, found typically in prokaryotes. Specifically, it binds with the S12 protein involved in the initiation of protein synthesis. Experiments have shown that streptomycin prevents the initiation of protein synthesis by blocking the binding of initiator N-formylmethionine tRNA to the ribosome. Streptyomycin is also known to prevent the normal dissociation of 70S ribosomes into their 50S and 30S subunits. Thus formation of polysomes is inhibited. The overall effect of streptomycin seems to involve distorting the ribosome so that transition from initiation complex (30S-mRNA-tRNA) to chain elongating ribosome is blocked. Thus, the normal sequence of translation is disrupted, the bacteria is unable to synthesize proteins vital for its cell growth and thereby fails to survive.
