title: The AGA1 product is involved in cell surface attachment of the Saccharomyces cerevisiae cell adhesion glycoprotein a-agglutinin.
abstract: Saccharomyces cerevisiae a and alpha cells express the complementary cell surface glycoproteins a-agglutinin and alpha-agglutinin, respectively, which interact with one another to promote cellular aggregation during mating. Treatment of S. cerevisiae a cells with reducing agents releases the binding subunit of a-agglutinin, which has been purified and characterized; little biochemical information on the overall structure of a-agglutinin is available. To characterise a-agglutinin structure and function, we have used a genetic approach to clone an a-agglutinin structural gene (AGAI). Mutants with a-specific agglutination defects were isolated, the majority of which fell into a single complementation group, called aga1. The aga1 mutants showed wild-type pheromone production and response, efficient mating on solid medium, and a mating defect in liquid medium; these phenotypes are characteristic of agglutinin mutants. The AGA1 gene was cloned by complementation; the gene sequence indicated that it could encode a protein of 725 amino acids with high serine and threonine content, a putative N-terminal signal sequence, and a C-terminal hydrophobic sequence similar to signals for the attachment to glycosyl phosphatidylinositol anchors. Active a-agglutinin binding subunit is secreted by aga1 mutants, indicating that AGA1 is involved in cells surface attachment of a-agglutinin. This result suggests that AGA1 encodes a protein with functional similarity to the core subunits of a-agglutinin analogs from other budding yeasts. Unexpectedly, the AGA1 transcript was expressed and induced by pheromone in both a and alpha cells, suggesting that the a-specific expression of active a-agglutinin results only from a-specific regulation of the a-agglutinin binding subunit.
authors.affiliation: Department of Biological Sciences, Columbia University, New York, New York 10027.
authors.forename: A
authors.initials: A
authors.lastname: Roy
authors.forename: C F
authors.initials: CF
authors.lastname: Lu
authors.forename: D L
authors.initials: DL
authors.lastname: Marykwas
authors.forename: P N
authors.initials: PN
authors.lastname: Lipke
authors.forename: J
authors.initials: J
authors.lastname: Kurjan
mesh_terms: D000371:Agglutination; D000595:Amino Acid Sequence; D001483:Base Sequence; D015815:Cell Adhesion Molecules; D002462:Cell Membrane / Q000502:physiology; D003433:Crosses, Genetic; D004271:DNA, Fungal / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics*; D005799:Genes, Dominant; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D046911:Macromolecular Substances; D000072235:Mating Factor; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010455:Peptides / Q000378:metabolism*; D010675:Pheromones / Q000378:metabolism; D011487:Protein Conformation; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
chemical_list: C543384:AGA1 protein, S cerevisiae; D015815:Cell Adhesion Molecules; D004271:DNA, Fungal; D005656:Fungal Proteins; D046911:Macromolecular Substances; D010455:Peptides; D010675:Pheromones; D029701:Saccharomyces cerevisiae Proteins; C069939:a-agglutinin protein, S cerevisiae; D000072235:Mating Factor