Structure and function of fungal adhesins

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A family of GPI-linked cell wall proteins, known as fungal adhesins, confers unique surface adhesion properties in the budding yeast Saccharomyces cerevisiae, the human pathogenic yeast Candida glabrata and the industrially relevant yeast Pichia pastoris. The detailed features of most of these proteins conferring surface discrimination and adherence were so far largely unknown. During the last funding period, we determined crystal structures of the adhesion domains of the S. cerevisiae floccu-lins Flo5 and Flo11 as well as of the C. glabrata adhesin Epa1 at atomic resolutions. For the next funding period, we propose to elucidate the structural and functional properties of further carbohy-drate-binding adhesins from S. cerevisiae, C. glabrata and P. pastoris in vitro and in vivo. Specifically, we will analyze N-terminal ligand-binding domains of selected members from the C. glabrata Epa and Pwp families and of Flo5-related putative adhesins from P. pastoris. Respective recombinant adhesin domains will be screened for specific ligand binding by glycan microarray analysis and subjected to crystallization and structure determination by X-ray crystallographic analysis. The in vivo properties of the different adhesin ligand-binding domains will further be investigated by functional analysis using S. cerevisiae as a heterologous system. We will also determine the biochemical properties of the central, repetitive B domains of fungal adhesins, whose structures and functions are not known in detail yet, by using the S. cerevisiae flocculin Flo5 as a model.