Protein G

Protein G is a cell surface protein that exists in different molecular forms, typically around 60 kDa in size. The native form of Protein G also binds to albumin, but this binding site has been removed in recombinant versions to reduce non-specific binding . Recombinant Protein G is often expressed in Escherichia coli (E. coli) and can be modified with tags such as polyhistidine (His) for easier purification and detection .

Protein G has a high affinity for the Fc region of IgG antibodies from various species, including humans, rabbits, and mice. This binding specificity makes it particularly useful for purifying antibodies from complex mixtures and for detecting antibodies in various assays .

1. Antibody Purification: Protein G is widely used to purify IgG antibodies from serum, cell culture supernatants, and other sources. The recombinant form, which lacks the albumin-binding site, ensures higher purity of the isolated antibodies .
2. Immunoprecipitation: Protein G is used to precipitate antigen-antibody complexes, allowing researchers to isolate and study specific proteins from a mixture.
3. Immunofluorescence and Super-Resolution Imaging: Recombinant Protein G, labeled with fluorophores or single-stranded DNA, can replace secondary antibodies in imaging techniques, providing more precise and specific detection .

• Reduced Non-Specific Binding: The removal of the albumin-binding site in recombinant Protein G minimizes non-specific interactions, leading to cleaner results in antibody purification and detection .
• High Purity and Stability: Recombinant Protein G is typically produced with high purity (>98%) and can be stored for extended periods without significant loss of activity .
• Versatility: The ability to modify recombinant Protein G with various tags and labels enhances its utility in different experimental setups .