Bacterial 50S ribosomal subunit peptidyl transferase center and nascent peptide exit tunnel (50S PTC/NPET)

The bacterial 50S ribosomal subunit peptidyl transferase center (PTC) and the proximal nascent peptide exit tunnel (NPET) are essential functional domains within the large subunit of the bacterial ribosome (Wikipedia, 2024). The PTC, located in domain V of the 23S rRNA, serves as the catalytic site for peptide bond formation, effectively functioning as a ribozyme (NIH, 2024). Adjacent to the PTC is the NPET, a narrow channel through which the growing polypeptide chain must pass to reach the exterior of the ribosome (PNAS, 2018). These regions are the primary targets for numerous clinically significant antibiotic classes, including macrolides, lincosamides, oxazolidinones, and pleuromutilins (MDPI, 2024). While PTC-binding drugs typically block the chemical catalysis of translation, NPET-binding drugs like macrolides physically obstruct the exit path, often leading to ribosome stalling in a sequence-dependent manner (Cell, 2012). Therapeutic challenges include the emergence of resistance through rRNA mutations or methylation and potential off-target toxicity due to the structural resemblance between bacterial and human mitochondrial ribosomes (BioRxiv, 2024).

Other names

50S ribosomal subunit23S rRNA peptidyl transferase centerBacterial large ribosomal subunitRibosomal exit tunnelPTCNPET23S ribosomal RNA

Antibiotics targeting these sites inhibit protein synthesis by either blocking the catalytic formation of peptide bonds at the peptidyl transferase center (PTC) or physically obstructing the passage of the nascent polypeptide chain through the nascent peptide exit tunnel (NPET) (NIH, 2024; PNAS, 2018). PTC inhibitors like chloramphenicol and lincosamides compete with the aminoacyl-tRNA for binding, while NPET inhibitors like macrolides cause ribosome stalling and premature peptidyl-tRNA dissociation (MDPI, 2024; Cell, 2012).