Mating type-specific cell-cell recognition of Saccharomyces cerevisiae: cell wall attachment and active sites of a- and alpha-agglutinin.
Mating type-specific agglutination of Saccharomyces cerevisiae a and alpha cells depends on the heterophilic interaction of two cell surface glycoproteins, the gene products of AG alpha 1 and AGA2. Evidence is presented with immunogold labelling that the alpha-agglutinin is part of the outer fimbrial cell wall coat. The a-agglutinin is bound via two S-S bridges (Cys7 and Cys50) to a cell wall component, most probably the gene product of AGA1. His273 of alpha-agglutinin has previously been shown to be essential for a- and alpha-agglutinin interaction and a model based on two opposing ion-pairs had been proposed. By site-directed mutagenesis this possibility has now been excluded. With the help of various peptides, either chemically synthesized, obtained by proteolysis of intact glycosylated a-agglutinin or prepared from a fusion protein expressed in Escherichia coli, the biologically active region of a-agglutinin was located at the C-terminus of the molecule. A peptide consisting of the C-terminal 10 amino acids (GSPIN-TQYVF) was active in nanomolar concentrations. Saccharide moieties, therefore, are not essential for the mating type-specific cell-cell interaction; glycosylated peptides are, however, four to five times more active than non-glycosylated ones. Comparisons of the recognition sequences of the S. cerevisiae agglutinins with that of the Dictyostelium contact site A glycoprotein (gp80), as well as with those of the various families of cell adhesion molecules of higher eucaryotes, have been made and are discussed.
Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Universität Regensburg, Germany.
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Cappellaro
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Baldermann
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Rachel
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Tanner
D000373:Agglutinins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002448:Cell Adhesion / Q000502:physiology*; D015815:Cell Adhesion Molecules; D002473:Cell Wall / Q000378:metabolism*; D005656:Fungal Proteins / Q000502:physiology; D000072235:Mating Factor; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins
C543384:AGA1 protein, S cerevisiae; C543385:AGA2 protein, S cerevisiae; D000373:Agglutinins; D015815:Cell Adhesion Molecules; D005656:Fungal Proteins; D010455:Peptides; D029701:Saccharomyces cerevisiae Proteins; C069939:a-agglutinin protein, S cerevisiae; D000072235:Mating Factor