2.)  Co-Immunoprecipitation

This technique works by using an antibody which immunoprecipitate the respective antigen and with it co - immunoprecipitate any interacting protein. The protein molecules involved in the complex formation must be bound tightly to each other so that on being pulled, entire complex can be precipitated out. The method checks the interaction in the protein complex in their natural conformation. However one disadvantage is that sometimes concentration of the antigen gets lower thus unable to be detect ed effeciently (Fig. 2.).

Important steps involved in Co-immunoprecipitation technique

1. Antibody- Antigen selection

It is very important to select specific antigen and antibody (for precipitating the antigen bounded with protein of interest), for easy and specific precipitation. Sometimes it happens that the antibody precipitate a non specific protein other than desired antigenic protein.

2. Cellular lysis procedure.

Care should also be taken during the cellular lysis procedure as not to disturb the proteins complex. The lysis procedure should be mild.

Figure 1: Diagrammatic representation of protein-protein interaction studies by co-immunoprecipitation