The<unk>  <unk>  is a technique for studying protein-protein interactions.  It involves creating a fusion protein with a designed piece, the<unk>  tag, on the end.  The protein of interest with the<unk>  tag first binds to beads coated with IgG, the<unk>  tag is then broken apart by an enzyme, and finally a different part of the<unk>  tag binds reversibly to beads of a different type.  After the protein of interest has been washed through two affinity columns, it can be examined for binding partners.
The<unk>  method involves the fusion of the<unk>  tag to the C-terminus of the protein under study. The<unk>  tag consists of calmodulin binding peptide (CBP) from the N-terminal, followed by tobacco etch virus protease (TEV protease) cleavage site and Protein A, which binds tightly to IgG. The relative order of the modules of the tag is important because Protein A needs to be at the extreme end of the fusion protein so that the entire complex can be retrieved using an IgG matrix.
Tandem affinity purification
Affinity chromatography
Molecular cloning
Quantitative proteomics
Enzyme linked immunosorbent assay 
Surface-enhanced laser desorption/ionization
Enzyme assay
Direct fluorescent antibody