Determining Protein-Protein Interaction with GFP-Trap Beads.

Protein-protein interactions play a vital role in the cellular physiology of living organisms. Among several available approaches, co-immunoprecipitation (co-IP) has emerged as a reliable method to investigate such interactions. The underlying principle is to retrieve a bait protein from a protein extract using bait-specific antibodies and thereby indirectly capture the interacting partner proteins. However, bait-specific antibodies are not always available, and the genetic fusion of a peptide tag offers an alternative. An extensive range of peptide tags and the tag-specific antibodies are available nowadays. Fluorescent proteins are widely used protein tags for co-IP experiments. In this chapter, we describe a method to co-immunoprecipitate the fluorescently tagged candidate protein with its interacting partners from the crude plant cell extracts using green fluorescent protein (GFP)-trap magnetic beads.