tap tag coimmunoprecipitation true tap tag coip PSI-MI MI:0109 The TAP method involves the fusion of the TAP tag (encoding a calmodulin binding peptide, a TEV cleavage site, and the Staphylococcus aureus Protein A) to the target protein and the introduction of the construct into the host cell or organism, maintaining the expression of the fusion protein at, or close to, its natural level. The fusion protein and associated components are recovered from cell extracts by affinity selection on an IgG matrix. After washing, the TEV protease is added to release the bound material. The eluate is incubated with calmodulin-coated beads in the presence of calcium. This second affinity step is required to remove the TEV protease as well as traces of contaminants remaining after the first affinity selection. After washing, the bound material is released with EGTA. This two steps purification steps ensures a highly selective complex purification of the tapped protein (first round of selection on the protein A, a high affinity tag) under mild condition (non denaturant pH or conditions required to remove the tag). OBSOLETE redundant term. Map to feature type: tap tagged (MI:0524) and as interaction detection method tandem affinity purification (MI:0676).