Post-translational modification

Post-translational modifications can occur on the amino acid side chains or at the protein's C- or N- termini.

[1] They can expand the chemical set of the 22 amino acids by changing an existing functional group or adding a new one such as phosphate.

[6] Sites that often undergo post-translational modification are those that have a functional group that can serve as a nucleophile in the reaction: the hydroxyl groups of serine, threonine, and tyrosine; the amine forms of lysine, arginine, and histidine; the thiolate anion of cysteine; the carboxylates of aspartate and glutamate; and the N- and C-termini.

[15] In 2011, statistics of each post-translational modification experimentally and putatively detected have been compiled using proteome-wide information from the Swiss-Prot database.

PTM information can be collected through experimental means or predicted from high-quality, manually curated data.

Post-translational modification of insulin . At the top, the ribosome translates a mRNA sequence into a protein, insulin, and passes the protein through the endoplasmic reticulum , where it is cut, folded, and held in shape by disulfide (-S-S-) bonds. Then the protein passes through the golgi apparatus , where it is packaged into a vesicle. In the vesicle, more parts are cut off, and it turns into mature insulin.
Flowchart of the process and the data sources to predict PTMs. [ 26 ]
Effect of PTMs on protein function and physiological processes. [ 32 ]