What is bait protein?

In the context of molecular biology and biochemistry, a bait protein refers to a protein that is used to capture or "bait" a specific target protein or protein complex of interest in a laboratory setting. It serves as a "fishing hook" to selectively bind and isolate the target protein from a complex mixture of proteins, usually within a cell lysate or tissue extract.

The bait protein is typically engineered or modified to have a high affinity for the target protein. This interaction can be achieved through various strategies, such as:

Antibody-Based Bait Proteins: Antibodies or antibody fragments can be used as bait proteins if they specifically recognize and bind to the target protein. The antibody bait can be immobilized on a solid support, such as beads or magnetic particles, allowing for efficient capture of the target protein.

Tagged Bait Proteins: The bait protein can be genetically engineered to carry a specific affinity tag, such as a FLAG-tag, His-tag, or GST-tag. These tags enable the bait protein to be immobilized or purified using corresponding capture reagents or chromatography resins, which have specific binding properties for the tags.

Protein Interaction Domains: Bait proteins can be engineered to contain protein interaction domains that specifically bind to the target protein. For instance, if the target protein contains a PDZ domain, the bait protein can be designed to have a PDZ-binding motif.

The bait protein is then used in a technique called "pull-down assay" or "co-immunoprecipitation" to capture the target protein. The cell lysate or tissue extract is incubated with the bait protein immobilized on a solid support, allowing the target protein to bind to the bait. After extensive washing to remove unbound components, the bound proteins are eluted, and the presence of the target protein is confirmed through various analytical methods, such as Western blotting or mass spectrometry.

By utilizing bait proteins, researchers can selectively isolate and study specific proteins or protein complexes of interest, providing valuable insights into their molecular interactions, functions, and roles in biological processes.