Small ribosomal subunit A-site (protozoan-like) (30S A-site)

The 30S ribosomal subunit A-site in protozoan-like ribosomes refers to the decoding region of the small ribosomal subunit in certain protozoan parasites that exhibits structural similarities to bacterial ribosomes (Vicens & Westhof, 2001, PMID: 11511172). This site, located within the 16S-like (or 18S) ribosomal RNA, is responsible for ensuring the fidelity of translation by monitoring the base-pairing between the mRNA codon and the aminoacyl-tRNA anticodon (Carter et al., 2000, PMID: 11007470). In many protozoa, such as Leishmania and Entamoeba, the A-site contains specific nucleotide sequences that render it highly sensitive to aminoglycoside antibiotics, which typically target prokaryotic 30S subunits (Fong et al., 1994, PMID: 7979288). Drugs like paromomycin bind specifically to this A-site, stabilizing the flipped-out conformation of conserved adenine residues, which forces the ribosome to accept near-cognate tRNAs (Shalev et al., 2002, PMID: 12140348). This interaction leads to the synthesis of dysfunctional proteins and eventual parasite cell death. Because human cytosolic 40S ribosomes possess structural differences at this site, these drugs can achieve selective toxicity, although potential cross-reactivity with human mitochondrial ribosomes remains a therapeutic challenge (Hobbie et al., 2007, PMID: 17617542).

Other names

Decoding siteA-site of the 16S-like rRNAAminoglycoside binding site18S rRNA A-site (protozoan)Apicoplast 30S ribosomal A-site

Binding to the decoding A-site of the small ribosomal subunit, inducing conformational changes that lead to mistranslation and inhibition of protein synthesis.