50S bacterial ribosomal subunit (50S subunit) (50S subunit)

The 50S bacterial ribosomal subunit is the larger component of the prokaryotic 70S ribosome, primarily composed of the 23S ribosomal RNA (rRNA), the 5S rRNA, and approximately 33 ribosomal proteins [1]. Its central biological role is to catalyze the formation of peptide bonds between amino acids during translation, a process mediated by the peptidyl transferase center (PTC) located within the 23S rRNA [2]. Additionally, the subunit forms the nascent peptide exit tunnel (NPET), which guides the growing polypeptide chain away from the catalytic site [3]. This subunit is a major therapeutic target for several classes of antibiotics, including macrolides, lincosamides, oxazolidinones, and pleuromutilins, which selectively bind to the rRNA to disrupt protein synthesis [4]. Because bacterial ribosomes are structurally distinct from eukaryotic 80S ribosomes, these drugs achieve selective toxicity, although their similarity to human mitochondrial ribosomes can lead to clinical side effects like myelosuppression [5]. Resistance to these agents frequently occurs through point mutations in the 23S rRNA or enzymatic modifications such as methylation, which hinder drug binding [6].

Other names

23S ribosomal RNA5S ribosomal RNALarge ribosomal subunitBacterial 50S ribosomeProkaryotic 50S subunit

Inhibition of bacterial protein synthesis by binding to the 23S rRNA component of the 50S subunit, which either blocks the peptidyl transferase center (PTC) to prevent peptide bond formation or obstructs the nascent peptide exit tunnel (NPET) to trigger premature dissociation of peptidyl-tRNA [4, 7].