Investigation of Lectin Binding.

Carbohydrate binding proteins are important messengers in the signalling between cells and are involved in important cellular processes such as protein translocation, differentiation and maturation. At Carlsberg Laboratory a study was performed on sialic acid binding siglec 1, a macrophage surface protein, obtained from Paul Crocker at University of Dundee, was studied in order to find high affinity ligands from a sialic acid containing glycopeptide library. Ligands were found that bound with 10 fold higher affinity than the natural ligands and after resynthesis one ligand was crystallized with the protein to provide the crystal structure of the glycopeptide bound to siglec 1. In a similar study libraries of glycopeptides were screened with the lectin domain of GalNAc transferases affording active ligands binding to the lectin domain. The assay in which binding is studied involves the labelling of an expressed protein and purification followed by incubation of the glycopeptide library on PEGA or SPOCC resin. Fluorescent beads are then isolated using fluorescence activated bead sorting providing high affinity ligands for the lectin of interest.