16S ribosomal RNA A-site (16S rRNA A-site) (16S rRNA A-site)

The 16S ribosomal RNA (rRNA) A-site is a highly conserved and functionally essential region within the 30S small subunit of the bacterial ribosome (Nature, 1987). It serves as the decoding center where the ribosome monitors the fidelity of codon-anticodon pairing between messenger RNA (mRNA) and aminoacyl-transfer RNA (tRNA) (Wikipedia, 2024). During translation, key adenine residues (A1492 and A1493) undergo conformational changes to stabilize correct tRNA binding (NIH, 2024). This site is a major therapeutic target for several classes of antibiotics, including aminoglycosides and tetracyclines (StatPearls, 2023). Aminoglycosides bind to the A-site and lock these adenine residues in an active conformation, which promotes the incorporation of incorrect amino acids and leads to bacterial cell death (NIH, 2024). Tetracyclines act by sterically hindering the binding of aminoacyl-tRNA to the A-site, effectively stopping protein elongation (NIH, 2016). Resistance is frequently mediated by 16S rRNA methyltransferases or specific point mutations that reduce drug affinity (NIH, 2024).

Other names

Decoding centerDecoding siteAminoacyl site30S A-site16S rRNA decoding region

Antibiotics targeting the 16S rRNA A-site typically inhibit protein synthesis by either sterically blocking the entry of aminoacyl-tRNA (e.g., tetracyclines) or by binding to the decoding center to induce conformational changes that cause mRNA misreading and mistranslation (e.g., aminoglycosides) (Nature, 1987; NIH, 2024).