Flocculation protein structure and cell–cell adhesion mechanism in Saccharomyces cerevisiae

Abstract

Cell-cell adhesion occurs in a broad spectrum of biological processes, of which yeast flocculation is an area of interest for evolutionary scientists to brewers and winemakers. The flocculation mechanism is based on a lectin-carbohydrate interaction but is not yet fully understood, although the first model dates back to the 1950s. This review will update the current understanding of the complex mechanism behind yeast flocculation. Moreover, modern technologies to measure the forces involved in single carbohydrate-lectin interactions, are discussed. The Flo1 protein has been extensively described as the protein responsible for strong flocculation. Recently, more research has been directed to the detailed analysis of this flocculin. Due to the advances in the field of bioinformatics, more information about Flo1p could be obtained via structurally or functionally related proteins. Here, we review the current knowledge of the Flo1 protein, with a strong emphasis towards its structure.

Architecture and Biosynthesis of the Saccharomyces cerevisiae Cell Wall

“…The first contains those with the potential to participate in wall construction as hydrolases or transglycosidases. The second contains nonenzymatic agglutinins, flocculins, or b1,3-glucan cross-connectors (Klis et al , 2010Dranginis et al 2007;Goossens and Willaert 2010). Most, if not all the proteins in these two groups are glycosylated.…”

“…Both groups contain GPI proteins. Cell wall proteins have been reviewed by Klis et al (2002, Lesage and Bussey (2006), and Gonzalez et al (2009), glycosylhydrolases by Adams (2004), agglutinins by Dranginis et al (2007), and flocculins by Goossens and Willaert (2010). Additional information about these proteins is presented in File S9.…”

“…Flocculins and agglutinins: GPI-CWP involved in cell-cell adhesion are the related Flo1, Flo5, Flo9, Flo10, and Flo11/ Muc1 flocculins, the Aga1 and Fig2 pair, and the a-agglutinin Sag1 (Roy et al 1991;Cappellaro et al 1994;Chen et al 1995;Caro et al 1997;Erdman et al 1998;Guo et al 2000;Shen et al 2001;Dranginis et al 2007;Van Mulders et al 2009;Goossens and Willaert 2010).…”

“…Major features are N-terminal PA14 domains that bind a-mannosides and mediate adhesion to adjacent cells, a central Ser/Thr-rich domain that is organized in repeat sequences and heavily glycosylated, and two or three conserved three-Cys repeats toward their C termini (Verstrepen and Klis 2006;Goossens and Willaert 2010;Klis et al 2010;Veelders et al 2010;Goossens et al 2011). In addition, the Ser/Thr-rich domains of Flo1 and Flo11/Muc1 have short sequences enriched in Ile, Thr, and Val that are predicted to form intramolecular b-sheetlike interactions or amyloids, and both a soluble, GPI-less portion of Flo11/Muc1 and a Flo1-derived form fibrillar b-aggregates in vitro (Ramsook et al 2010).…”

The mannose-specific lectin domains of Flo1p fromSaccharomyces cerevisiaeand Lg-Flo1p fromS. pastorianus: crystallization and preliminary X-ray diffraction analysis of the adhesin–carbohydrate complexes

“…This phenomenon is very familiar to brewers as a simple and economic system to separate yeast cells from beer at the end of the primary fermentation. Yeast flocculation has been extensively investigated during the last half century using the model yeast Saccharomyces cerevisiae (Verstrepen & Klis, 2006;Goossens & Willaert, 2010;Brü ckner & Mö sch, 2012). The formation of yeast flocs generally takes place under starvation conditions (i.e.…”