Tag:BLRP is an artificial 23 amino acid residue peptide (MASSLRQILDSQKMEWRSNAGGS) that can be biotinylated efficiently in vivo by the Ecol\birA biotin ligase (biotinylation occurs on the K residue of the tag). The biotinylated tag can then be used as an affinity tag for one-step purification, by binding to streptavidin, of the tagged protein or its complexes (PMID:12802011).