SARS-CoV-2 S Protein and ACE2 Binding Assays

The SARS-CoV-2 S protein and ACE2 binding assay is performed with surface plasmon resonance (SPR) technology measuring the direct binding of potential therapeutics to the S protein receptor-binding domain or ACE2. The assay is suitable to determine whether a test molecule(s) disrupts the S protein /ACE2 interaction including kinetic parameters. 

We can investigate two targeting strategies: 1. The development of molecules that occupy the host cell’s ACE2 receptors to prevent the virus from attaching. 2. The development of molecules that bind and saturate the S protein on the virus surface such that binding to ACE2 is limited or cannot occur.

  • Probe the direct binding kinetics (on/off-rate and KD) to optimize target engagement (on-rate) and residence time on the target (off-rate)
  • New drug candidates can be tested with a throughput of up to 2300 compounds per day.

S Protein – ACE2 Interaction

SARS-CoV-2 is lined with large spike (S) proteins that engage the host cell protein ACE2 (Angiotensin-converting enzyme 2), which serves as a receptor for virus entry. After binding to ACE2, the virus enters the host cell via membrane fusion either with the cell membrane or after endocytosis.

Coronavirus entry into cells with focus on S protein and ACE2 receptor interaction showing different options for intervention of SARS-CoV-2 host cell entry

Assay Details

Example MLN-4760

surface plasmon resonance assay for testing the interaction of S protein and ACE2 receptor for compound testing of SARS-CoV-2 therapeutics

Surface plasmon resonance for the detection of binding of MLN-4760 to ACE2: In order to directly probe the binding kinetics of small molecules to ACE2, relatively high levels of the target on the sensor chip are needed (due to the large difference in mass between these molecules and the protein target). To achieve these higher levels, ACE2 was covalently attached to the sensor chip via amine coupling. To validate that the target is binding competent once immobilized to the sensor chip, the binding of ACE2 inhibitor MLN-4760 was measured using a kinetic titration (single-cycle kinetics).  The KD value of ~1 nM is consistent with the IC50 value of 440 pM.


To learn more about surface plasmon resonance (SPR), please visit our biophysics assays webpage.