A fusion tag called FLAG consists of eight amino acids (Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys). FLAG is specifically designed for immunoaffinity chromatography. It allows elution under non-denaturing conditions. Several antibodies against this peptide have been developed. One antibody denoted as M5 detects N-terminal Met-FLAG fusion proteins.
Anti-FLAG (M5)-SAP is a chemical conjugate of a mouse monoclonal antibody to the N-terminal Met-FLAG fusion protein and the ribosome-inactivating protein, saporin. It specifically eliminates cells with extracellular expression of FLAG-tagged proteins and cells that recognize YOUR FLAG-tagged recombinant proteins.