Surface plasmon resonance imaging-based protein arrays for high-throughput screening of protein-protein interaction inhibitors

The E7 protein produced by high‐risk human papillomavirus (HPV) induces a degradation of the retinoblastoma tumor suppressor RB through direct interaction, which suggests that an inhibitor for the interaction can be a potential anticancer drug. A surface plasmon resonance (SPR) imaging‐based protein array chip was developed for the high‐throughput screening of inhibitor molecules targeting RB‐E7 interaction. The glutathione S‐transferase‐fused E7 protein (GST‐E7) was first layered onto a glutathionylated gold chip surface that had been designed to specifically bind to GST‐fused proteins. Subsequently, a microarrayer was used to spot the hexa‐histidine‐tagged RB proteins (His6‐RB) onto the GST‐E7‐layered gold chip surface, and the resulting SPR image was analyzed. Upon increased His6‐RB concentration in the spotting solution, the SPR signal intensity increased proportionally, indicating that His6‐RB bound to GST‐E7 in a concentration‐dependent manner. The His6‐RB/GST‐E7 interaction was challenged by spotting the His6‐RB solution in the presence of a RB binding peptide (PepC) derived from a motif on E7. The SPR imaging data showed that PepC inhibited the His6‐RB/GST‐E7 interaction in a concentration‐dependent manner. Our results show that the SPR imaging‐based protein array chip can be applied to screen small molecule inhibitors that target protein‐protein interaction.