Protein A used for the purification of IgG is isolated from:
Protein A used for the purification of IgG is isolated from:
Select an option to attempt
Correct Answer: Option A
Explanation
Protein A from Staphylococcus aureus — IgG purification:Protein A is a surface protein from S. aureus cell wall that has an extraordinary property:• Binds with very high affinity to the Fc region of IgG antibodies from many mammalian species (especially human, mouse, rabbit IgG).• Binding is through the CH2-CH3 hinge region of the Fc portion.Application in antibody purification:• Protein A-Sepharose affinity columns are the gold standard for purifying IgG.• Crude serum/culture supernatant is loaded → IgG binds to Protein A → contaminants washed away → IgG eluted with low pH buffer (pH 2.5–3.0) or high salt.• Achieves >95% purity in one step.Note: Protein G (from Streptococcus) also binds Fc but with slightly different species specificity.Answer: Protein A (from S. aureus) binds the Fc region of IgG; used for one-step IgG affinity purification.