LIGAND-BINDING ANALYSIS OF SOLUBLE INTERLEUKIN-2 RECEPTOR COMPLEXES BY SURFACE-PLASMON RESONANCE

Knowledge of the kinetic binding characteristics is often critical to the development of ligand/receptor structure-activity relationships, T o better understand the contribution of each of the subunits to ligand binding in the multimeric interleukin-2 receptor system, we have prev iously prepared stable solution complexes of the alpha- and beta subun its. In this study, we have employed surface plasmon resonance biosens or methodology (BLAcore(TM)) to evaluate both the kinetic and equilibr ium binding constants for these complexes, The structural nature of th e complexes facilitated immobilization on the sensor surfaces in a man ner that minimized interference with ligand interactions. The interleu kin-2 receptor complex surfaces displayed excellent binding capacity a nd stability toward regeneration. In all eases where the binding const ants were measurable, the values determined for interleukin-2 were in good agreement with those previously determined by other methods, When interleukin-2 analogs with receptor subunit specific mutations were e mployed, the binding parameters were consistent with the nature of the mutations. The combination of coiled-coil-mediated solution assembly and surface plasmon resonance analysis of ligand binding provides a po werful approach to the study of multimeric cytokine receptor systems.