Ribosome peptidyl transferase center–nascent peptide chain complex (PTC-NC complex)

The ribosome peptidyl transferase center (PTC)–nascent peptide chain complex is the catalytic core of the ribosome responsible for synthesizing proteins by forming peptide bonds. Located within the large ribosomal subunit (50S in bacteria, 60S in eukaryotes), the PTC acts as a ribozyme that precisely positions the peptidyl-tRNA and aminoacyl-tRNA for catalysis (Steitz & Moore, 2003). As the nascent peptide chain grows, it traverses the ribosomal exit tunnel, where its sequence can interact with the ribosome to regulate translation or respond to small-molecule drugs (Wilson, 2014). This complex is a major target for diverse classes of antibiotics, such as macrolides, oxazolidinones, and lincosamides, which obstruct the exit tunnel or the PTC itself to halt bacterial growth (Beringer & Rodnina, 2007). Furthermore, the PTC-NC complex is a target for nonsense suppression therapies, like ataluren, which aim to treat genetic disorders by allowing the ribosome to read through premature stop codons (Peltz et al., 2013). Therapeutic development focuses on maximizing selectivity for bacterial or specific mutant complexes to avoid interfering with host mitochondrial or cytoplasmic translation. The structural dynamics of the nascent chain within the tunnel also influence cotranslational protein folding and the recruitment of chaperones. Resistance to drugs targeting this complex often arises through mutations in ribosomal RNA or the presence of ribosomal protection proteins.

Other names

Peptidyl transferase centerRibosome-nascent chain complexRNCPTCLarge ribosomal subunit active site

Inhibition of peptide bond formation, steric hindrance of the nascent peptide exit tunnel, and modulation of translational read-through at premature stop codons.