Protein A ELISA Kit

Protein A affinity chromatography is commonly used in monoclonal antibody (mAb) manufacturing workflows due to its high binding affinity and the purity of the product obtained with it (1). There are occasions when Protein A or its fragments are filtered from a purification column and remain bound to the Fc region of a therapeutic antibody. This must be avoided, particularly in cases where the antibodies are manufactured for clinical uses in order to avoid any adverse effect of residual protein A on the patient.

R&D Systems has developed two ELISA kits for the reliable delivery and accurate detection of Protein A residues in the manufacture of therapeutic monoclonal antibodies, one for native and recombinant protein A and the other for modified variants of Protein A. These kits have been designed with a simplified procedure, precise quantification and allow easy transfer to automated platforms.


  • calibrated to Natural or Engineered protein A
  • Ready-to-use components including tampons
  • One-step sample pretreatment
  • Minimum test incubations
  • Consistent Supply and technical support


This ELISA detects non-natural constructs of Protein A, such as the MabSelect SuRe™ ligand sold by GE Healthcare. Use this kit if you are using a recombinant form of Protein A with significant structural differences from native Protein A, such as MabSelect SuRe™.

Four newer Protein A Elisa Kit assays known as Mix-N-Go™ methods are also available. These methods replace the sample boiling and centrifugation steps with a special sample treatment reagent that allows accurate detection of Protein A in the presence of antibodies from your sample. The Protein A Mix-N-Go™ Kit (F610) uses calibrated standards for non-natural protein A constructs such as MabSelect SuRe™ from GE Healthcare. The Protein A Mix-N-Go™ Kit (F600) uses standards calibrated against natural and conserved recombinant forms of Protein A.

What is Protein A?

Product Information

Product Type: ELISA Kit

Storage: All kit reagents 2°C to 8°C

Assay format: 96-well plate

Time to result: ~3 hrs. 40 minutes

LOD: ~50 pg/mL

LLOQ: 100 pg/mL

Recommended thinner: I028

What is Protein A?

Protein A, also known as Staphylococcus aureus protein A (SpA), is a 40-60 kDa surface protein originally found in the cell wall of Staphylococcus aureus bacteria. The carboxyl terminus of Protein A is anchored to the staphylococcal cell wall by the enzyme transpeptidase sortase. It is encoded by the spa gene and consists of five homologous immunoglobulin domains of 6.7 kDa (E, D, A, B, and C) joined by conserved linkers of six to nine residues. Protein A has been shown to stimulate inflammatory responses by interacting with several proteins, including tumour necrosis factor receptor alpha, Willebrand factor, and C1qR.

Protein A is best known for interacting with the Fc region of the heavy chain of the antibody. Although it binds to all mouse immunoglobulin (IgG) subtypes (IgG1, IgG2a, IgG2b, and IgG3), in humans it binds to IgG1, IgG2, and IgG4 but not to IgG3. Protein A does not bind IgG3 due to a single change from histidine to arginine at amino acid 435. Protein A reacts with Ig from a variety of other species, including the rhesus monkey, guinea pig, pig, cow, and goat.

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