Binding characterisation of the Saccharomyces cerevisiae flocculation protein Flo1p: Flo1p – Flo1p and Flo1p – mannose carbohydrate interactions

S. cerevisiae cells possess a remarkable capacity to adhere to other cells, which is called flocculation. These cell-cell-interactions are mediated by a class of special cell wall proteins, called flocculins that are anchored to the cell wall by a GPI-anchor. Flocculins consist of three domains and the first one is the mannose binding domain. We have studied the N-terminal domain of the Flo1-protein (N-Flo1p). It was shown that the protein is heavily glycosylated. The binding of N-Flo1p to different mannose-derivates was studied using fluorescence spectroscopy. It was found that N-Flo1p has a higher affinity for dimannoses than for monomannose and that the affinity also depends on the type of glycosidic bond between the two mannoses. This result indicates that the binding is more specific for certain mannose-containing glycans. Furthermore, the N-Flo1p to N-Flo1p binding was analysed using Surface Plasmon Resonance, and a lower binding capacity was observed when the protein was deglycosylated (N-glycans).