Protein Interactions

We offer a number of products for the analysis of protein interactions, including pull-down assays, BRET-based and complementation reporter-based systems.

GST pull-down systems are used in traditional methods based on cell extracts and/or cell-free expression. The HaloTag® Mammalian Pull-Down System is used to isolate and identify intracellular protein complexes from mammalian cells.

NanoBRET™ and NanoBiT® technologies provide methods for direct analysis of protein interactions in live cells. The NanoBRET™ System uses bioluminescence resonance energy transfer (BRET) in a proximity-based assay that detects protein interactions by measuring energy transfer from a bioluminescent protein donor to a fluorescent protein acceptor.

NanoBiT® assays rely on a two-subunit system based on NanoLuc® luciferase that can be used for intracellular detection of protein:protein interactions. The subunits are fused to proteins of interest, forming a functional enzyme that generates a bright, luminescent signal when the proteins interact.
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An Introduction to Protein Interactions

Protein:protein interactions (PPIs) are essential to almost every process in a cell, so understanding PPIs is crucial for understanding cell biology in normal and disease states. There are numerous methods used to characterize protein interactions that use cell extracts or live cells to express potential targets.

In a pull-down assay, one protein partner is expressed as a fusion protein (e.g., bait protein) in E. coli and then immobilized using an affinity ligand specific for the fusion tag. The immobilized bait protein can then be incubated with the prey protein.

Co-immunoprecipitation is another option to study protein:protein interactions. To perform co-immunoprecipitation, an antibody against a target protein is coupled to Sepharose® beads through protein A or G, and then the complexes containing the target protein are immunoprecipitated with the antibody-coupled beads.

However, these traditional methods for studying interactions between proteins do not provide data directly in the context of a cellular environment. Using Bioluminescence Resonance Energy Transfer (BRET) or complementation assays, it is possible to quantitatively measure the interaction between proteins in live cells.