What is co-immunoprecipitation?

Co-immunoprecipitation (Co-IP) is a technique used to identify protein-protein interactions. It involves using an antibody specific to a known protein ('bait' protein) to indirectly isolate other proteins ('prey' proteins) that are bound to it in a cell lysate. The antibody-protein complex is then pulled down (precipitated) using beads, and the associated proteins are identified, often by Western blotting or mass spectrometry.