Bacterial 16S ribosomal RNA helix 44 aminoacyl-tRNA site (16S rRNA h44 A-site)

The bacterial 16S ribosomal RNA helix 44 aminoacyl-tRNA site (A-site) is a fundamental component of the 30S small ribosomal subunit, serving as the primary location for mRNA decoding during protein synthesis (Ogle et al., 2001, Science). This region is responsible for ensuring the accuracy of translation by discriminating between cognate and non-cognate tRNA molecules through specific conformational changes in conserved adenine residues, A1492 and A1493 (Vicens & Westhof, 2001, Structure). In the presence of a correct codon-anticodon match, these residues flip out of the helix to stabilize the interaction, signaling the ribosome to proceed with peptide bond formation. This site is the principal target for aminoglycoside antibiotics, which bind to the decoding loop and lock it into a state that accepts incorrect tRNAs, resulting in the synthesis of erroneous and toxic proteins (PubMed: 11557972). Because of its essential role in bacterial viability, it is a high-priority target for treating severe Gram-negative and certain Gram-positive infections. However, the structural similarity between the bacterial A-site and the human mitochondrial 12S rRNA A-site is a major factor in the characteristic side effects of drugs targeting this region, such as hearing loss and kidney damage (Guan et al., 2000, Hum Mol Genet).

Other names

16S rRNA decoding siteHelix 44 of the 30S ribosomal subunitA-site of the 16S rRNADecoding region of the 30S subunith44 decoding center

Aminoglycosides bind to the internal loop of helix 44 of the 16S rRNA, inducing a conformational change in residues A1492 and A1493 that mimics proper codon-anticodon pairing (Ogle et al., 2001, Science). This leads to the incorporation of incorrect amino acids (mistranslation) and the inhibition of ribosomal translocation, ultimately resulting in bacterial cell death (Vicens & Westhof, 2001, Structure).