Protein A is a cell wall component produced by several strains of Staphylococcus aureus that consists of a single polypeptide chain and contains little or no carbohydrate. The Protein A molecule contains four high-affinity binding sites capable of interacting with the Fc region from IgG of several species including human and rabbit. Optimal binding occurs at pH 8.2, although binding is also effective at neutral or physiological conditions (pH 7.0 to 7.6).
Contains four Fc-binding domains per protein
Better than Protein G for polyclonal IgG from rabbit, pig, dog and cat serum
Poorer than Protein G for mouse IgG1, human IgG3 and rat, goat and cow antibodies