Analysis of the Ligand Recognition Specificities of Human Ficolins Using Surface Plasmon Resonance.

Abstract

Ficolins are innate immune recognition proteins involved in activation of the lectin complement pathway. These oligomeric lectin-like proteins are assembled from subunits consisting of a collagen-like triple helix and a trimeric fibrinogen-like recognition domain. In humans, three ficolins coexist: they differ in their ligand binding specificities, but share the capacity to associate with proteases through their collagen-like stalks and trigger complement activation. We describe methods to decipher the recognition specificities of ficolins, based on surface plasmon resonance, an optical technique allowing real-time and label-free monitoring of biomolecular interactions. This technique was mainly used to characterize and compare binding of the three recombinant full-length ficolins and of their isolated recognition domains to various immobilized BSA-glycoconjugates, acetylated BSA or biotinylated heparin. The avidity phenomenon that enhances the apparent affinity of interactions between oligomeric lectin-like proteins and the multivalent ligands is also discussed.