Bacterial 16S ribosomal RNA aminoacyl-tRNA site (16S rRNA A-site) (16S rRNA A-site)

The bacterial 30S ribosomal subunit's 16S rRNA A-site (aminoacyl-tRNA site) is a fundamental component of the bacterial translation machinery, serving as the decoding center where the fidelity of protein synthesis is maintained [3, 11]. It functions by monitoring the base-pairing between the mRNA codon and the tRNA anticodon, utilizing universally conserved adenine residues (A1492 and A1493) to stabilize correct matches [3, 11]. This site is a major therapeutic target for several classes of bactericidal and bacteriostatic antibiotics, including aminoglycosides and tetracyclines [1, 15, 18]. Aminoglycosides bind to the A-site to induce conformational changes that promote the incorporation of incorrect amino acids, leading to lethal mistranslation, while tetracyclines prevent the entry of aminoacyl-tRNAs altogether [1, 2, 18]. However, the clinical utility of drugs targeting this site is often limited by severe side effects, such as ototoxicity and nephrotoxicity, which arise from cross-reactivity with the highly similar human mitochondrial 12S rRNA [6, 18]. Additionally, the rapid spread of 16S rRNA methyltransferases among pathogenic bacteria has led to high-level resistance, necessitating the development of next-generation inhibitors [4, 6, 13].

Other names

Decoding siteAminoacyl-tRNA site30S A-site16S rRNA decoding centerHelix 44 of 16S rRNA

Aminoglycosides bind to the 16S rRNA A-site, inducing a conformational change in residues A1492 and A1493 that stabilizes the binding of non-cognate tRNAs, leading to mRNA misreading and mistranslation [1, 3, 6]. Tetracyclines bind to the A-site to sterically block the docking of aminoacyl-tRNAs, thereby inhibiting the elongation phase of protein synthesis [7, 18].