Practice question

Principle of pull-down assay centers on affinity binding between tagged bait protein and immobilized ligand, enabling capture of interacting prey proteins from mixture. Bait is expressed as fusion with GST, His, biotin, or Flag tag and retained on corresponding resin. Incubation with cell lysate allows physiological binding partners to co-precipitate via non-covalent interactions. After washing non-specific proteins, complex is eluted and analyzed by SDS-PAGE, Western blot, or mass spectrometry. Method does not depend on temperature-sensitive dyes, fluorescent resonance energy transfer, or radioactive labeling, but on highly specific tag-ligand affinity chemistry.