17-03-2017, 10:47 AM
FLAG, or FLAG epitope, is a polypeptide protein tag that can be added to a protein using recombinant DNA technology, having the sequence motif DYKDDDDK (where D = aspartic acid, Y = tyrosine and K = lysine). It has been used to study proteins in living cells and for purification of proteins by means of affinity chromatography. It has been used to separate the overexpressed recombinant protein from the wild-type protein expressed by the host organism. It can also be used in the isolation of complexes of proteins with multiple subunits, because its gentle purification procedure tends not to alter such complexes. It has been used to obtain proteins of sufficient purity and quality to carry out the determination of the structure in 3D by X-ray crystallography.
A FLAG tag can be used in many different assays requiring recognition by an antibody. If there is no antibody to a given protein, the addition of a FLAG tag to a protein allows the protein to be studied with an antibody against the FLAG sequence. Examples are cell localization studies by immunofluorescence or detection by SDS PAGE electrophoresis and Western blotting.