One common example of post-translational modification (PTM) of a protein is phosphorylation. In this process, a phosphate group is added to the amino acid residue of a protein, often targeting serine, threonine, or tyrosine residues. Phosphorylation can significantly affect the protein's function, activity, location, and interactions with other molecules.
Phosphorylation is a crucial mechanism in cellular signaling and regulation. For instance, many enzymes are activated or inhibited through phosphorylation, which plays a key role in processes such as cell division, growth, and metabolism. This modification is typically carried out by enzymes known as kinases and reversed by phosphatases.