The ribosome is the large 2.5 megadalton nucleoprotein complex that is responsible for messenger RNA-directed protein synthesis in all organisms. It has two subunits in all species. The small or 30S subunit is responsible for binding mRNA and ensuring the fidelity of translation, whereas the large or 50S subunit catalyzes peptide bond formation. The structure reveals a wealth of details about RNA and protein structure and protein-RNA interactions. The structure also allows us to infer details of its interactions with tRNA and mRNA ligands.
Many natural antibiotics target various aspects of ribosome function.
In a manner similar to classical enzyme inhibitors, these antibiotics have the potential to shed light not just on their own mode of action, but also on the mechanisms of translation. The structure of the 30S subunit has been solved with several antibiotics and an initiation factor. This has led to a concrete model for how the ribosome discriminates between tRNA in decoding.