Protein–Protein Interactions: Co-Immunoprecipitation

  • Jer-Sheng Lin
  • Erh-Min LaiEmail author
Part of the Methods in Molecular Biology book series (MIMB, volume 1615)


Proteins often do not function as single substances but rather as team players in a dynamic network. Growing evidence shows that protein–protein interactions are crucial in many biological processes in living cells. Genetic (such as yeast two-hybrid, Y2H) and biochemical (such as co-immunoprecipitation, co-IP) methods are the methods commonly used at the beginning of a study to identify the interacting proteins. Immunoprecipitation (IP), a method using a target protein-specific antibody in conjunction with Protein A/G affinity beads, is a powerful tool to identify molecules that interact with specific proteins. Therefore, co-IP is considered to be one of the standard methods of identifying or confirming the occurrence of protein–protein interaction events in vivo. Co-IP experiments can identify proteins via direct or indirect interactions or in a protein complex. Here, we use Agrobacterium type VI secretion system (T6SS) sheath components TssB-TssC41 interaction as an example to describe the principle, procedure, and experimental problems of co-IP.

Key words

Protein–protein interaction Immunoprecipitation (IP) Co-immunoprecipitation (Co-IP) Immobilization Protein A/G Sepharose Physical interaction 



This work was supported by a research grant from the Taiwan Ministry of Science and Technology (MOST 104-2311-B-001-025 -MY3) to E.M. Lai. J.S. Lin is the recipient of postdoctoral fellowships from Academia Sinica.


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© Springer Science+Business Media LLC 2017

Authors and Affiliations

  1. 1.Institute of Plant and Microbial BiologyAcademia SinicaTaipeiTaiwan

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