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

The 50S ribosomal subunit is the larger component of the prokaryotic 70S ribosome, found in bacteria and the apicoplast of Apicomplexan parasites like Plasmodium falciparum (Dahl & Rosenthal, 2007). It serves as the site of the peptidyl transferase center, which catalyzes the formation of peptide bonds during protein translation (Wilson, 2014). In parasites, the apicoplast is an essential organelle derived from an ancient endosymbiotic event, and its 50S subunit is critical for expressing the organelle's genome, which encodes vital metabolic enzymes (Fichera & Roos, 1997). Numerous classes of antibiotics, including macrolides, lincosamides, and oxazolidinones, exert their antimicrobial and antiparasitic effects by binding to the 23S rRNA within the 50S subunit (Bottger et al., 2001). This binding typically obstructs the ribosomal exit tunnel or prevents the proper positioning of aminoacyl-tRNA, thereby halting protein synthesis. In the context of malaria, inhibition of the apicoplast 50S subunit leads to a "delayed death" effect, where the parasite's progeny fail to survive due to the inheritance of non-functional apicoplasts (Dahl & Rosenthal, 2007). While these drugs are highly selective for the prokaryotic-like 50S subunit over the human 80S ribosome, their potential to cross-react with human mitochondrial ribosomes can lead to clinical safety concerns such as bone marrow suppression (Wilson, 2014).

Other names

Large ribosomal subunitProkaryotic 50S ribosomal subunitApicoplast 50S ribosomal subunit70S ribosome large subunit

Inhibition of protein synthesis by binding to the 23S ribosomal RNA of the 50S subunit, which blocks the peptidyl transferase center or the ribosomal exit tunnel, preventing peptide bond formation and polypeptide elongation.