The N-terminal domain of the cell wall protein Als1p from Candida albicans has a lectin activity with specific affinity to fucose-containing glycans.

The ALS gene family of Candida albicans encodes at least eight large cell-surface glycoproteins that are implicated in the process of adhesion to host surfaces [1-2]. The N-terminal part of Als1 protein is substrate-specific and has been shown to bind to endothelial cells [2-3]. The host-pathogen interactions very often rely on lectin-carbohydrate binding. Until now, a specific binding of any Als protein to a carbohydrate has not been described.
The objective of this study was to determine if Als1p-N has a lectin activity. The recombinant, His-tagged Als1p-N was purified in Saccharomyces cerevisiae and subsequently subjected to a glycan array screening (Consortium for Functional Glycomics). The glycan array analysis revealed the specificity of the Als1p-N towards fucose-containing glycans. Furthermore, the binding kinetics for this interaction have been determined. The surface plasmon resonance technique was used to demonstrate that Als1p-N binds to fucose with an affinity typical for lectin-carbohydrate interaction having equilibrium dissociation constant (KD) in micromolar range.