The N-terminal domain of the Flo1 flocculation protein from Saccharomyces cerevisiae binds specifically to mannose carbohydrates

Katty Goossens, Catherine Stassen, Ingeborg Stals, Dagmara DONOHUE, Bart Devreese, Henri De Greve, Ronnie Willaert

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Saccharomyces cerevisiae cells possess a remarkable capacity to adhere to other yeast cells, which is called
flocculation. Flocculation is defined as the phenomenon wherein yeast cells adhere in clumps and sediment
rapidly from the medium in which they are suspended. These cell-cell interactions are mediated by a class of
specific cell wall proteins, called flocculins, that stick out of the cell walls of flocculent cells. The N-terminal
part of the three-domain protein is responsible for carbohydrate binding. We studied the N-terminal domain
of the Flo1 protein (N-Flo1p), which is the most important flocculin responsible for flocculation of yeast cells.
It was shown that this domain is both O and N glycosylated and is structurally composed mainly of -sheets.
The binding of N-Flo1p to D-mannose, -methyl-D-mannoside, various dimannoses, and mannan confirmed
that the N-terminal domain of Flo1p is indeed responsible for the sugar-binding activity of the protein.
Moreover, fluorescence spectroscopy data suggest that N-Flo1p contains two mannose carbohydrate binding
sites with different affinities. The carbohydrate dissociation constants show that the affinity of N-Flo1p for
mono- and dimannoses is in the millimolar range for the binding site with low affinity and in the micromolar
range for the binding site with high affinity. The high-affinity binding site has a higher affinity for lowmolecular-
weight (low-MW) mannose carbohydrates and no affinity for mannan. However, mannan as well as
low-MW mannose carbohydrates can bind to the low-affinity binding site. These results extend the cellular
flocculation model on the molecular level.
Original languageEnglish
Pages (from-to)110-117
Number of pages7
JournalEukaryotic Cell
Volume10
Publication statusPublished - 1 Jan 2011

Keywords

  • Saccharomyces cerevisiae
  • flocculation
  • Flo1 protein

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