The N-terminal domain of Als1 protein from Candida albicans binds to blood group antigens.

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 had not been described.
The objective of this study was to determine if Als1p-N has also 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 specifity of the Als1p-N to fucose alone and to fucose-containing glycans. Furthermore, the binding kinetics for this interaction has been determined. The surface plasmon resonance technique was used to demonstrate, that Als1p-N binds to fucose with affinity typical for lectin-carbohydrate interaction (KD in micromolar range).