Ribosome A-site

The **Ribosome A-site (Aminoacyl-tRNA site)** is one of the three tRNA binding sites of the ribosome, integral to the process of protein synthesis in all cells[5][7][9]. Situated at the interface of the ribosomal small and large subunits, the A-site accommodates incoming aminoacyl-tRNAs that base-pair with the codon exposed by the ribosome on the mRNA template. Successful pairing at the A-site enables the ribosome's catalytic center to catalyze peptide bond formation, elongating the nascent polypeptide[3][5][7]. The site is central to the fidelity of translation and is the target of a number of important antibacterial drugs that inhibit translation by preventing tRNA accommodation or inducing codon misreading. While the A-site itself is not a molecule or receptor in the classical sense, it is considered a valid therapeutic target within the larger ribosome complex. Nevertheless, the phrase "Ribosome A-site/protein synthesis machinery" is **imprecise**: the A-site is a site within the broader ribosome complex (the canonical therapeutic target would thus be "Ribosome" or, even more precisely, for antibiotics "Bacterial ribosome A-site"). The full protein synthesis machinery comprises many components, including tRNAs, rRNA, and various translation factors[4][5][6][10]. **Notes:** - "Ribosome A-site/protein synthesis machinery" conflates the A-site (a specific functional site) and the entire translation apparatus, which includes many macromolecules. For structured, canonical drug discovery ontologies, designate "Ribosome A-site" as a binding target or "Ribosome" as the molecular complex (with sub-targets as appropriate)[5][7]. - All ribosomes (bacterial, eukaryotic, mitochondrial) have an A-site; drugs generally target bacterial ribosome A-sites for selective antimicrobial action[9].

Other names

Aminoacyl-tRNA siteA site (of ribosome)Ribosomal A-site

Inhibition of tRNA binding (blocking aminoacyl-tRNA entry to the A-site); Induction of mRNA misreading; Inhibition of peptide bond formation (indirect, as a consequence of blocked A-site occupancy)