Distribution of the flocculation protein, Flop, at the cell surface during yeast growth: the availability of Flop determines the flocculation level

Abstract

The yeast FLO genes encode cell surface proteins which are expected to play a major role in the control of flocculation. We have assessed the availability of the Flo proteins at the cell surface during the growth of two flocculent strains, ABXL-1D (FLO1) and STX347-1D (FLO5) using immunological approaches, enzyme-linked immunosorbent assays and immunofluorescence. Our data show that they are not permanently present at the cell surface but that their amount increases during growth. With both strains the flocculation level is tightly correlated to the amount of Flop antigen detected, suggesting that it is the availability of the Flo proteins at the cell surface which determines the flocculation level. Our data are consistent with the idea that the Flo proteins correspond to the flocculation lectins. The differences of flocculation pattern among strains could originate from variations in the regulation of the expression of the FLO genes. Monitoring of the distribution of the Flo proteins during cellular development revealed that they are incorporated essentially in the cell wall of growing buds. Incorporation of the Flo proteins in the cell wall displays a highly polarized aspect, at the bud tip and at the mother-daughter neck junction, which can persist in mature cells. Such a localization could be relevant to constraints of the cell wall incorporation of the mannoproteins. Depending on the regulation of Flop expression and on the incorporation of the proteins in the cell wall, a yeast population can be highly heterogeneous in Flo protein equipment.

125th Anniversary Review: Yeast Flocculation and Sedimentation in Brewing

“…A rough cell surface topography is believed to favour cell to cell adhesion during the onset of flocculation 63 . Flocculins have been reported to be localised at the site of bud formation, so that mother cells may express a greater number of flocculins 7 . Moreover, cell surface hydrophobicity, which has a positive effect on flocculation, increases with replicative age.…”

Applications of yeast flocculation in biotechnological processes

“…Further evidence has shown that Flo1p was a true cell wall mannoprotein [45,46]. In agreement with this idea Bony and co-workers [47] showed that the availability of Flo proteins at the cell surface of yeasts is well correlated with the flocculation level, being its distribution at the cell surface dependent on the constraints of cell wall biogenesis. The study of the Flo1 protein indicated that the hydrophobic C-terminus, which is a putative GPI anchoring domain, is necessary for the anchoring of Flo1p in the cell wall [45] and that the Nterminal domain of the protein is responsible for sugar recognition [45,46].…”

“…These proteins are anchored in the cell wall with the C-terminus, while the N-terminal sugar-binding part is protruding in the medium [42,[44][45][46][47]. All strains containing these FLO genes belong to the Flo1 phenotype [34].…”

Distinctly Different Characteristics of Flocculation in Yeast1

“…1 A part of the contents of this paper was communicated as a poster presentation at the 10th International Yeast Symposium held in Arnhem, Netherlands in 2000. 2 Department of Chemistry, Faculty of Education, Kagawa University, 1-1 Saiwai-cho, Takamatsu 760-8522, Japan. 3 Corresponding author: E-mail: nishihar@ed.kagawa-u.ac.jp…”

“…A similar conclusion was reported through chemical modification of cell surface protein and carbohydrate of cells of beer yeast IFO 2018 from this laboratory 11 . Hitherto several papers have appeared which dealt with characteristics and function of the protein essential for yeast flocculation 1,2,4,6,14,18 . It was also reported that flocculation receptors were outer-chain mannan sidebranches, two or three mannose residues in length 16 .…”