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

The bacterial 16S ribosomal RNA (rRNA) decoding A-site is a critical functional region within the 30S small ribosomal subunit responsible for ensuring the fidelity of protein synthesis [PubMed: 11586302]. During translation, this site monitors the base-pairing between the mRNA codon and the aminoacyl-tRNA anticodon [PubMed: 10993070]. When a correct match occurs, specific adenine residues, A1492 and A1493, flip out of the internal loop of helix 44 to stabilize the interaction, signaling the ribosome to proceed with peptide bond formation [PubMed: 11012830]. This site is the primary therapeutic target for aminoglycoside antibiotics, such as gentamicin and amikacin, which bind to the internal loop and lock these adenine residues in the 'active' conformation [PubMed: 15916402]. This drug-induced conformational change causes the ribosome to accept near-cognate tRNAs, leading to the production of mistranslated, dysfunctional proteins that compromise bacterial cell membrane integrity [PubMed: 17626568]. Additionally, some drugs like tetracyclines bind to the 16S rRNA in the A-site to physically block the docking of aminoacyl-tRNA, thereby inhibiting protein synthesis [PubMed: 11130708]. Because the bacterial A-site structure is distinct from the human cytosolic ribosome, it allows for selective toxicity, although similarities with human mitochondrial 12S rRNA can lead to adverse effects like ototoxicity [PubMed: 12657573]. Resistance to drugs targeting this site often arises through enzymatic modification of the drugs or methylation of the 16S rRNA by specialized methyltransferases [PubMed: 17307851].

Other names

16S rRNA aminoacyl-tRNA binding siteDecoding region of 16S rRNA30S ribosomal A-siteHelix 44 of 16S rRNAA-site of the 30S subunit

Aminoglycosides bind to the 16S rRNA A-site, inducing a conformational change in residues A1492 and A1493 that mimics cognate tRNA binding, leading to mistranslation and membrane damage; Tetracyclines bind to the A-site to sterically block aminoacyl-tRNA attachment, inhibiting protein synthesis.