Bacterial 50S ribosomal subunit peptidyl transferase center and A-site (50S PTC/A-site)

The bacterial 50S ribosomal subunit peptidyl transferase center (PTC) and A-site constitute the catalytic core of the ribosome, essential for the synthesis of all bacterial proteins. The PTC is a ribozyme composed of 23S ribosomal RNA (rRNA) that facilitates the formation of peptide bonds between the growing polypeptide chain and incoming amino acids (Polikanov et al., 2014, Molecular Cell). The A-site (aminoacyl site) is the specific region where the aminoacyl-tRNA binds to the ribosome before the peptidyl transfer occurs (Wilson, 2014, Nature Reviews Microbiology). Because these regions are vital for bacterial viability and possess structural features distinct from eukaryotic cytoplasmic ribosomes, they serve as the primary target for several major classes of antibiotics, including macrolides, oxazolidinones, and lincosamides (Arenz & Wilson, 2016, Cold Spring Harbor Perspectives in Medicine). These drugs typically function by physically obstructing the PTC or interfering with the correct orientation of tRNA molecules, thereby halting translation. However, the structural homology between bacterial ribosomes and human mitochondrial ribosomes can lead to off-target effects and clinical toxicities, such as bone marrow suppression (Böttger et al., 2001, EMBO Reports). Resistance to these agents frequently arises through specific mutations in the 23S rRNA or enzymatic modification of the rRNA by methyltransferases (Long & Vester, 2003, Antimicrobial Agents and Chemotherapy).

Other names

23S rRNA peptidyl transferase centerRibosomal peptidyl transferase center50S A-siteRibosomal A-sitePTCLarge ribosomal subunit A-site

Inhibition of bacterial protein synthesis by sterically blocking the peptidyl transferase reaction or preventing the binding and positioning of aminoacyl-tRNA in the A-site.