Ribosome large subunit A-site (A-site)

The ribosome large subunit A-site (aminoacyl site) is a fundamental component of the translation machinery, serving as the primary entry point for aminoacyl-tRNA molecules during protein synthesis (Wilson, 2014). Located within the 50S subunit in prokaryotes and the 60S subunit in eukaryotes, the A-site is positioned adjacent to the peptidyl transferase center (PTC), the catalytic heart of the ribosome where peptide bonds are formed (Dunkle et al., 2010). This site is a major therapeutic target for several classes of antibiotics, including oxazolidinones (e.g., linezolid) and pleuromutilins (e.g., lefamulin), which bind to the 23S ribosomal RNA to block the proper positioning of incoming tRNAs (Paukner & Riedl, 2017). By disrupting the elongation phase of translation, these drugs effectively inhibit bacterial growth and are critical for treating multi-drug resistant infections such as MRSA (StatPearls, 2023). Because of the structural similarities between bacterial ribosomes and human mitochondrial ribosomes, drugs targeting this site can cause off-target effects such as myelosuppression during prolonged therapy (Nier et al., 2022). Understanding the structural nuances of the A-site is essential for developing new antimicrobial agents that can overcome emerging resistance mechanisms like the cfr methyltransferase (PubMed, 2012). Additionally, the A-site is a focus of research for nonsense mutation suppression therapies aimed at treating various genetic disorders (Nature, 2017).

Other names

Aminoacyl-tRNA binding siteAcceptor site50S A-site60S A-siteRibosomal A-siteAminoacyl site

Inhibition of protein synthesis by sterically blocking the binding of aminoacyl-tRNA to the ribosomal A-site or interfering with the peptidyl transferase reaction (Wilson, 2014; Paukner & Riedl, 2017).