Proteins are vital macromolecules that facilitate most biological processes at both cellular and systemic levels, but they rarely act alone. Lots of essential molecular processes are carried out by molecular machines based on a large number of protein components organized by their Protein-Protein Interactions (PPIs), which refer to intentional physical contacts established between two or more proteins as a result of biochemical events and/or electrostatic forces. Since the interactions are at the core of the entire interactomics system of any living cell, unsurprisingly, specific PPIs are on the basis of multiple diseases.
Figure 1. Protein-protein interaction hot spots and allosteric sites. (Turnbull A P. et al.; 2014)
The discovery or verification of an interaction of protein-protein interaction is the first step to understand where, how and under what conditions these proteins interact in vivo and the functional implications of these interactions. Currently, as shown in Table 1, there are some popular methods in PPI studies, which is critical to understand protein function and the biology of the cell.
Table 1. The most popular methods in PPI studies
|Method||Types of PPIs|
|Co-Immunoprecipitation (co-IP)||Stable or strong|
|Pull-Down Assay||Stable or strong|
|Crosslinking Protein Interaction Analysis||Transient or weak|
|Label Transfer Protein Interaction Analysis||Transient or weak|
|Far-Western Blot Analysis||Moderately stable|
Protein-Protein Interaction Analysis at Creative Proteomics
At Creative Proteomics, we can provide various techniques to study protein interactions. Each method has its own advantages and limits. We can help you choose the suitable method and perform the project. Our services include but are not limited to:
Co-IP is a useful in vitro method for proteins involved in the complex bind to each other tightly. It can identify PPIs by using target protein-specific antibodies to indirectly capture proteins that are bound to this specific target protein. Co-IP can capture and purify not only the primary target, but also other macromolecules binding to the target by native interactions.
The pull-down assay can determine a physical interaction between two or more proteins and identify previously unknown PPIs. In a pull-down assay, a bait protein is tagged and immobilized to affinity resin. When a sample incubates with the bait proteins, proteins binding to the bait protein can be captured and “pulled down”.
Crosslinking protein interaction analysis is suitable for transient or weak interaction, which can be performed in vivo or in vitro. In this method, analytical solution, like crosslinking reagents or crosslinkers, can capture protein-protein complexes by covalently binding them together as they interact for consequent isolation and characterization.
Label transfer is useful to identify transient or weak PPIs that are difficult to capture using other in vitro detection strategies. It studies PPIs by using a label transfer reagent to tag proteins that interact with a protein of interest. The development of new non-isotopic reagents and methods makes the label transfer analysis method more accessible and simpler to perform.
Far-western blot, based on the technique of western blot, can be used to detect in vitro PPIs, especially for interactions that do not require the native structure of the protein of interest. In this method, a purified and labeled "bait" proteins are used to probe and detect a target "prey" protein on the membrane.
The result of two or more proteins that interact with a specific functional objective can be demonstrated in several different ways. The measurable effects of protein interactions have been outlined as follows:
Creative Proteomics has a team of scientists with years of experience in protein-protein interaction studies, which can help you to study protein-protein interaction project and accelerate your research. Based on professional knowledge and experienced staff, Creative Proteomics offers a wide range of protein-protein interaction networks in a time-saving and cost-efficient manner. Our ordering procedure is as follows. If you have any questions or specific requirements, please feel free to contact us.
1. Turnbull A P, Boyd S M, Walse B. Fragment-based drug discovery and protein–protein interactions. Research and Reports in Biochemistry, 2014, 4: 13-26.