Surface Acoustic Waves-Based Molecular Recognition of a Collagen Receptor on Human Erythrocytes

Integrin-mediated binding is important for the metastatic dissemination of different types of cancer cells. Snake venom disintegrins obtustatin and echistatin are potent, irreversible, and selective inhibitors of α1β1 and αvβ3 integrins, respectively. Obtustatin is one of the shortest disintegrins yet described, containing 41 amino acids. It has a similar pattern of cysteines to the other disintegrin echistatin but with a KTS motif rather than a classic RGD in its active site. A surface acoustic wave biosensor was applied to prove the molecular recognition of disintegrins by their substrates. The human erythrocyte ghost cells were immobilized at the sensors to allow for the detection of kinetic binding constants of disintegrins compared to the surface of giant unilamellar vesicles (GUVs). Obtustatin binds to the erythrocyte ghost membrane with affinity in the mid-nanomolar range (2.32 × 10^-7 M), and echistatin in the low micromolar range, which indicates specific molecular recognition for both disintegrins, but the higher response for obtustatin. The data directly confirm that disintegrins bind to the erythrocyte ghost membrane, thereby supporting the previously overlooked presence of integrins in red blood cell membranes.