Ser19

Ser19 is a designation used in molecular biology to refer to the serine residue at position 19 in a protein sequence. Serine is one of the 20 standard amino acids, and residues are numbered from the N-terminus of the translated protein. The exact residue referred to as Ser19 depends on the protein and whether numbering is based on the nascent polypeptide or a mature, processed form, so Ser19 in one protein may correspond to a different region in another.

In many proteins, Ser19 is a site for post-translational modification, most commonly phosphorylation. Phosphorylation at Ser19 can influence protein activity, interactions with other proteins, subcellular localization, stability, or signaling outcomes. Evidence for Ser19 phosphorylation typically comes from mass spectrometry data, phospho-specific antibodies, or mutational analyses. Common experimental approaches include substituting serine with alanine (S19A) to prevent phosphorylation and with aspartate or glutamate (S19D/E) to mimic phosphorylation, as well as structural studies to assess local effects.

Context and conservation of Ser19 vary widely among proteins and species. Some proteins have documented Ser19 phosphorylation, while others do not. Databases such as UniProt and phosphoproteomics resources record reported Ser19 sites for specific proteins. Researchers reference Ser19 to discuss regulatory mechanisms, compare orthologs, or interpret phosphoproteomic results. See also: serine, phosphorylation, residue numbering.