PeptidyltransferaseCenter

Peptidyltransferase Center, often abbreviated as the PTC, is the catalytic heart of the ribosome responsible for peptide bond formation during protein synthesis. In bacteria, the PTC is located in domain V of the 23S ribosomal RNA of the large subunit; in eukaryotes it resides in the analogous region of the 28S rRNA. The center is formed primarily by ribosomal RNA and is conserved across life, with ribosomal proteins arranged around it to provide structural support. The active site is RNA-based, acting as a ribozyme, and catalysis involves conserved nucleotides and coordinated metal ions, notably magnesium, rather than amino acid side chains.

During translation, the PTC catalyzes the transfer of the nascent polypeptide chain from the peptidyl-tRNA in the P site to the aminoacyl-tRNA in the A site, forming a new peptide bond and extending the growing chain. After bond formation, the deacylated tRNA moves to the P site and the ribosome undergoes translocation to prepare for the next cycle. The PTC operates in concert with other ribosomal components and translation factors to ensure fidelity and efficiency of protein synthesis.

Evolutionarily, the PTC is highly conserved and regarded as one of the oldest catalytic centers in biology. Structural studies by X-ray crystallography and cryo-electron microscopy have illuminated its RNA-based architecture and its interactions with substrates and antibiotics. Because of its essential role, the PTC is a common target for antibacterial compounds that inhibit peptide bond formation, highlighting its central importance in cellular biology.