23S ribosomal RNA helix 69 (H69)

Helix 69 (H69) is a highly conserved, 19-nucleotide hairpin loop located within the 23S ribosomal RNA (rRNA) of the bacterial 50S subunit [10, 15]. It serves as a vital structural component of the intersubunit bridge B2a, which facilitates communication and association between the 50S and 30S ribosomal subunits by interacting with helix 44 of the 16S rRNA [2, 5, 7]. H69 is essential for multiple stages of protein synthesis, including translation initiation, tRNA selection at the A-site, and the recycling of ribosomal subunits after termination [4, 11, 15]. Its dynamic conformational flexibility is modulated by post-transcriptional modifications, such as pseudouridylation and methylation, which are critical for its proper function and drug binding affinity [1, 6, 14]. Due to its central role in ribosome assembly and activity, H69 is a primary or secondary target for several classes of antibiotics, including aminoglycosides like neomycin and tuberactinomycins like capreomycin [1, 12, 21]. These drugs bind to H69 to inhibit protein synthesis by freezing the ribosome in specific states or preventing the dissociation of subunits [2, 17, 21].

Other names

Helix 69H6923S rRNA H69Intersubunit bridge B2a component

Inhibition of protein synthesis by disrupting ribosome dynamics, including subunit association, translocation, and recycling, often by stabilizing specific ribosomal states or inducing steric clashes with tRNA.