What is the Difference Between Immunoprecipitation and Coimmunoprecipitation

The main difference between immunoprecipitation and coimmunoprecipitation is that antibodies precipitate specific target antigens in immunoprecipitation, whereas antibodies precipitate antigens with their binding partners in coimmunoprecipitation.

Immunoprecipitation and coimmunoprecipitation are two immunoassays. They precipitate specific antigens from samples.

Key Areas Covered

1. What is Immunoprecipitation
– Definition, Process, Importance
2. What is Coimmunoprecipitation
– Definition, Process, Importance
3. Similarities Between Immunoprecipitation and Coimmunoprecipitation
– Outline of Common Features
4. Difference Between Immunoprecipitation and Coimmunoprecipitation
– Comparison of Key Differences

Key Terms  

Coimmunoprecipitation, Immunoprecipitation

What is Immunoprecipitation

Immunoprecipitation is precipitating proteins from the solution using antibody-specific binding to the target protein. It is important to isolate and concentrate the proteins from a solution among thousands of proteins. Moreover, its antibodies are coupled to a solid substrate. However, the technique is important in individual protein immunoprecipitation, protein complex immunoprecipitation, chromatin immunoprecipitation, ribonucleoprotein immunoprecipitation, and tag proteins.

Figure 1: Immunoprecipitation

Furthermore, the three immunoprecipitation methods include direct, indirect, and selection. The direct immunoprecipitation method uses antibodies specific to the target protein to immobilize it on a solid surface. The indirect immunoprecipitation method uses antibodies specific to a group of proteins for immobilization. Moreover, the selection method is important when the target protein concentration is low in a solution.

Also, in immunoprecipitation, antibodies are added to the mixture of antigens to form antigen-antibody complexes. Then, the antigen-antibody complex is immobilized with primary and secondary antibodies or antibodies coated with beads. Next, antigens can be eluted from beads in an acidic solution or SDS. An exception for antibodies for the precipitation of target molecules is His tag and other recombinant DNA technologies. 

What is Coimmunoprecipitation

Coimmunoprecipitation is another technique used to purify target antigens from a mixture. The key feature of coimmunoprecipitation is that it precipitates the target protein with its binding partners. Therefore, the target antigen is called the bait protein, while its binding partners are called prey proteins. Importantly, it precipitates a target protein as a member of a large protein complex. Also, it pulls the entire protein complex with unknown members. Some proteins bind to other proteins to form complexes, and this binding is tight.

Figure 2: Coimmunoprecipitation

Moreover, coimmunoprecipitation is a gold-standard assay for protein-protein interactions. On the other hand, it is an affinity purification method. It separates molecules according to the binding interactions with a ligand. Also, it purifies bio-specific ligands. In coimmunoprecipitation, specific antibodies are added to the protein extract. It immunoprecipitates the bait protein with prey proteins. Then, antibodies are coupled to beads. It isolates the protein complexes. 

However, coimmunoprecipitation is a more straightforward technique to study protein-protein interactions. Separose beads are the type of beads coupled with antibodies in the technique. Further, centrifugation is the technique used to separate coprecipitated protein complexes. Also, western blotting is used to visualize different components of the protein complex.  

Similarities Between Immunoprecipitation and Coimmunoprecipitation

• Immunoprecipitation and coimmunoprecipitation are two immunoassays used to precipitate antigens from samples.
• They use antigen-antibody interactions to precipitate target antigens. 

Difference Between Immunoprecipitation and Coimmunoprecipitation

Definition

Immunoprecipitation refers to an immunoassay used to separate proteins that are bound to a specific antibody from the rest of a sample. In contrast, coimmunoprecipitation refers to immunoassays used to identify protein-protein interactions between the protein that binds to the antibody.

Function

Antibodies precipitate specific target antigens in immunoprecipitation, while antibodies precipitate antigens with their binding partners in coimmunoprecipitation.

Importance

Immunoprecipitation precipitates only a single protein, while coimmunoprecipitation precipitates protein complexes. 

Conclusion

In brief, immunoprecipitation and coimmunoprecipitation are two immunoassays. They precipitate proteins using antibody-antigen interactions. However, immunoprecipitation precipitates a target protein with the use of specific antibodies. Therefore, it only precipitates a single protein. In comparison, coimmunoprecipitation precipitates a target protein along with its binding partners. Importantly, it precipitates complex proteins. Hence, the main difference between immunoprecipitation and coimmunoprecipitation is the precipitation type. 

References:

1. The principle and method of immunoprecipitation (IP). Centers for Disease Control and Prevention. 
2. EMBL-EBI. (2022b, October 24). Co-immunoprecipitation Centers for Disease Control and Prevention. 

Image Courtesy:

1. “Immunoprecipitation” By Dtabb73 – Own Work (CC0) via Commons Wikimedia
2. “20110113-Co-Immunoprecipitation” By Itayba at Hebrew Wikipedia – Own work (CC-BY SA 3.0) via Commons Wikimedia