Phosphorylation is the addition of a phosphate (PO4) group to a protein molecule or a small molecule.
Its prominent role in biochemistry is the subject of a very large body of research.
Phosphorylation usually occurs on serine, threonine, and tyrosine residues in eukaryotic proteins.
Antibodies can be used as powerful tools to detect whether a protein is phosphorylated at a particular site. Antibodies bind to and detect phosphorylation-induced conformational changes in the protein. Such antibodies are called phospho-specific antibodies. They are becoming critical reagents both for basic research and for clinical diagnosis.