Immunoassay technique to detect a change or molecular interaction of a specific protein. The protein of interest is first immunoprecipitated from a cell lysate using an antibody specific to it. This antibody-protein mixture is then incubated with agarose beads coupled with G proteins (these proteins have the particularity of a strong antibodies binding). Beads are heavier and can be separated by centrifugation.
After isolation from a complex mixture (cell lysate) of a protein of interest, it’s loaded on a SDS-PAGE. By a Western blot procedure, detection of the protein with a different antibody allow to highlight a modification or an interaction.