Kinetic measurement of the interaction between an oligosaccharide and lectins by a biosensor based on surface plasmon resonance

Abstract

Kinetic measurements of the interaction between an oligosaccharide and various lectins were performed using a biosensor based on surface plasmon resonance (SPR). A glycopeptide, prepared from asialofetuin and having a nearly homogeneous N-linked sugar chain, was immobilized on the surface of a sensor chip via the amino groups of its peptide moiety. The interactions of this bound glycopeptide with six lectins [Sambucus sieboldiana lectin, Maackia amurensis lectin, Aleuria aurantia lectin, Ricinus communis agglutinin-120 (RCA₁₂₀), Datura stramonium lectin (DSA) and Phaseolus vulgaris leukoagglutinating lectin] were monitored in real-time with the change in the SPR response. Of these lectins, only RCA₁₂₀ and DSA showed an increase in the SPR response, indicating that these two lectins bound specifically to the immobilized glycopeptide. The other lectins did not show any significant changes in the SPR response. These results are in good agreement with the binding specificity previously demonstrated with affinity chromatography. The association-rate constant (k_ass) and the dissociation-rate constant (k_diss) for the glycopeptide-RCA₁₂₀ interaction were 3.4 × 10⁵ M⁻¹ s⁻¹ and 2.1 × 10⁻³ s⁻¹, respectively. The k_ass and k_diss determined for DSA were 5.7 × 10⁵ M⁻¹ s⁻¹ and 1.3 × 10⁻³ s⁻¹, respectively. Furthermore, the relative binding molar ratio to the glycopeptide was three times higher for RCA₁₂₀ than for DSA, suggesting that this sugar chain possesses three binding sites for RCA₁₂₀ and one for DSA. These parameters are expected to provide useful information for defining the interaction between oligosaccharides and lectins.