This term should only be used to annotate a protein modification process that occurs after the protein has been released from the ribosome, and is therefore strictly post-translational. Modification of a free protein (one not attached to a ribosome) and modification of a C-terminal residue are post-translational processes. Some protein modifications occur while the protein is still in the ribosome but before translation has been completed; these modification processes are considered co-translational and should not be annotated using this term.

The process of covalently altering one or more amino acids in a protein after the protein has been completely translated and released from the ribosome.

posttranslational amino acid modification

posttranslational modification

posttranslational protein modification

PTM

post-translational modification

post-translational amino acid modification

biological_process

GO:0043687