Mycobacterial 50S ribosomal subunit, peptidyl-tRNA site (P-site) (50S P-site)

The Mycobacterial 50S ribosomal subunit, P-site (peptidyl-tRNA site) is a vital functional domain within the large subunit of the ribosome in mycobacterial species, including Mycobacterium tuberculosis. Its primary biological role is to accommodate the tRNA molecule attached to the nascent polypeptide chain, facilitating the peptidyl transferase reaction and subsequent translocation during protein synthesis (Wilson, 2014, PubMed). This site is the primary target for the oxazolidinone class of antibiotics, such as linezolid and tedizolid, which bind to the 23S rRNA at the peptidyl transferase center (PTC) to inhibit the formation of the 70S initiation complex (Hentschel et al., 2017, Nature). By disrupting the translation process, these drugs exert a bacteriostatic or bactericidal effect, making the P-site a cornerstone in the treatment of multi-drug resistant tuberculosis (MDR-TB). However, because the P-site shares structural similarities with the human mitochondrial ribosome, prolonged use of drugs targeting this site can lead to mitochondrial dysfunction and associated toxicities like myelosuppression and neuropathy (StatPearls, 2023). Resistance to P-site inhibitors often involves point mutations in the 23S rRNA or enzymatic modification by methyltransferases, which reduce drug binding affinity (NCBI, 2022).

Other names

Peptidyl-site of the 50S ribosomeMycobacterial 50S P-site23S rRNA P-siteMycobacterial large ribosomal subunit P-sitePeptidyl transferase center P-site

Inhibition of protein synthesis by binding to the P-site and adjacent peptidyl transferase center of the 50S ribosomal subunit, thereby preventing the formation of the functional 70S initiation complex and interfering with the translocation of peptidyl-tRNA (Wilson, 2014, PubMed).