This subsection of the ‘PTM/processing’ section describes post-translational modifications (PTMs). This subsection complements the information provided at the sequence level or describes modifications for which position-specific data is not yet available.
A post-translational modification is a covalent processing event resulting from a proteolytic cleavage or from the addition of a modifying group to one amino acid. So far, more than 200 PTMs have been characterized. They modulate the function of most eukaryote proteins by altering their activity state, localization, turnover, and interactions with other proteins.
Although proteins can be modified pre-, co- or post-translationally, all protein modifications are generally referred to as PTMs, because a majority of them are made post-translationally, after the protein is folded.