Surface plasmon resonance imaging analysis of protein–protein interactions using on-chip-expressed capture protein

A surface plasmon resonance (SPR) imaging system, combined with a microwell gold chip for on-chip cell cultivation, was used to monitor protein–protein interactions. In particular, we developed an on-chip microscale cell cultivation system that integrates cell culture and on-chip analysis of protein–protein interactions on a single microwell chip in a time- and labor-saving manner. To assess the performance of this system in the analysis of protein–protein interactions, we conducted a series of protein–protein interaction analyses by measuring the binding of the yeast GAL4 dimerization domain (GAL4DD) to the GAL11 protein (GAL11P). Our system was found to enable the simple and rapid analysis of protein–protein interactions, requiring no special cell culturing equipment or recombinant protein expression prior to the immobilization of the purified proteins onto the chip. Our results demonstrate that the combination of an on-chip cell cultivation system and an SPR imaging system can be a useful tool to study protein–protein interactions without the need for time-consuming and labor-intensive protein preparation steps as well as fluorescent or other labeling of the interactants.