Chemical Structure from Scientific Research

Schematic depicting peptide bond formation in the ribosome active site known as the PTC. The PTC promotes peptide bond formation by positioning the nucleophilic -amino group (N ) of one substrate, the A-site aminoacyl-tRNA, near the electrophilic sp 2 -hybridized carbonyl carbon (C sp 2 ) of the second substrate, the P-site peptidyl-tRNA. Attack by N generates a tetrahedral intermediate that subsequently breaks down to product: a peptidyl-tRNA carrying an additional C-terminal amino acid. Cytidine residues of the tRNAs' 3'-CCA ends are represented by the letter 'C' in a yellow circle.

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