The recombinant Protein A/G-Cys is a genetically engineered protein containing 5 IgG-binding regions of protein A and 2 of protein G. Additionally there is a C-terminal cysteine for Site-Specific Conjugation. Cell wall binding region, cell membrane binding region and albumin binding region have been removed from the recombinant A/G-Cys to ensure the maximum specific IgG binding. The recombinant Protein A/G-cys is ideal for making affinity gel to purification of polyclonal or monoclonal IgG antibodies. Protein A/G binds to various human, mouse and rat IgG subclasses (e.g., human IgG1, IgG2, IgG3, IgG4; mouse IgG2a, IgG2b, IgG3; rat IgG2a, IgG2c) . It also binds to total IgG from cow, goat, sheep, house, rabbit, guinea pig, pig, dog and cat.