title: Fluorescence polarization as a tool to study lectin-sugar interaction. An investigation of the binding of 4-methylumbelliferyl beta-D-galactopyranoside to Abrus precatorious agglutinin.
abstract: Polarization of ligand fluorescence was used to study the binding of 4-methylumbelliferyl beta-D-galactopyranoside (MeUmb-Galp) to Abrus precatorious agglutinin. The binding of the fluorescent sugar to the lectin led to considerable polarization of the MeUmb-Galp fluorescence, which was also quenched by about 30% on binding to the lectin. The binding of the fluorescent sugar was carbohydrate-specific, as evidenced by inhibition of both fluorescence polarization and quenching when lectin was preincubated with lactose. The association constant as determined by fluorescence polarization is 1.42 x 10(4) M-1 at 25 degrees C and is in excellent agreement with those determined by fluorescence quenching (Ka = 1.51 x 10(4) M-1) and equilibrium dialysis (Ka = 1.62 x 10(4) M-1) at 25 degrees C. The numbers of binding sites as determined by fluorescence polarization, quenching and equilibrium dialysis agree very well with one another, n being equal to 2.0 +/- 0.05. The consistency between the association constant value determined by fluorescence polarization, quenching and equilibrium dialysis shows the validity of this approach to study lectin-sugar interaction.
mesh_terms: D001665:Binding Sites; D003956:Dialysis; D005454:Fluorescence Polarization; D005697:Galactosides; D006027:Glycosides; D006923:Hymecromone / Q000031:analogs & derivatives; D037102:Lectins; D013050:Spectrometry, Fluorescence; D014468:Umbelliferones
chemical_list: D005697:Galactosides; D006027:Glycosides; D037102:Lectins; D014468:Umbelliferones; D006923:Hymecromone; C026845:4-methylumbelliferyl-galactopyranoside