Bacterial 16S ribosomal RNA helix 44 (h44)

Helix 44 (h44) is a prominent and highly conserved structural element of the 16S ribosomal RNA (rRNA) within the bacterial 30S ribosomal subunit [15]. It plays a fundamental role in the decoding process of protein synthesis by forming the core of the aminoacyl-tRNA binding site (A-site) [7, 9]. During translation, h44 facilitates the monitoring of codon-anticodon complementarity; specifically, nucleotides A1492 and A1493 flip out of the helix to stabilize correct tRNA binding [3, 6, 7]. This region is the primary therapeutic target for aminoglycoside antibiotics, such as gentamicin and amikacin, which bind to the internal loop of h44 [4, 5]. By binding here, these drugs induce a conformational state that mimics cognate tRNA recognition, leading to the incorporation of incorrect amino acids and the production of non-functional proteins [1, 3, 6]. While highly effective against a broad range of bacteria, the structural similarity between bacterial h44 and the human mitochondrial 12S rRNA decoding site can lead to significant clinical toxicities, including ototoxicity and nephrotoxicity [1, 7, 11]. Consequently, h44 remains a focal point for the development of next-generation antibiotics designed to overcome bacterial resistance mechanisms like rRNA methylation [4, 13].

Other names

16S rRNA helix 44h44Decoding siteRibosomal A-site30S ribosomal subunit helix 44

Aminoglycoside antibiotics bind to the decoding center within helix 44 of the 16S rRNA, inducing a conformational change in nucleotides A1492 and A1493 that mimics correct codon-anticodon pairing [3, 6, 7]. This leads to translational misreading (miscoding) and/or the inhibition of translocation, resulting in the synthesis of aberrant proteins and bacterial cell death [1, 3, 4, 6, 11].