A-site on 16S ribosomal RNA of the bacterial 30S ribosomal subunit (16S rRNA A-site)

The A-site on 16S ribosomal RNA of the bacterial 30S ribosomal subunit is a highly conserved, functionally crucial region within the small subunit of the prokaryotic ribosome responsible for the accurate decoding of mRNA via codon-anticodon interactions. The 16S rRNA itself is the main RNA component of the 30S subunit and serves as a scaffold for ribosomal proteins, but the A-site is specifically where incoming aminoacyl-tRNA is selected and paired with the mRNA codon. Key nucleotides within the site—G530, A1492, and A1493—undergo conformational changes that ensure high fidelity in tRNA selection and prevent incorporation of incorrect amino acids. This site is a primary therapeutic target for several antibiotics, notably aminoglycosides and tetracyclines, which interfere with bacterial protein synthesis by binding to the A-site, thereby inducing misreading of mRNA or blocking tRNA entry, respectively. Due to its essential role, mutations at the A-site are associated with antibiotic resistance and may serve as molecular biomarkers. As an RNA structural target, it is distinct from classical proteinaceous drug targets and represents a key node in the central dogma of molecular biology and infectious disease therapy.

Other names

Aminoacyl-tRNA binding site on 16S rRNADecoding site of 16S rRNA30S ribosomal A-site

Aminoglycosides bind to the A-site, distorting its structure, inducing misreading of mRNA and inhibiting protein synthesis. Tetracyclines block the binding of aminoacyl-tRNA to the A-site, inhibiting translation.