AG alpha 1 is the structural gene for the Saccharomyces cerevisiae alpha-agglutinin, a cell surface glycoprotein involved in cell-cell interactions during mating.
We have cloned the alpha-agglutinin structural gene, AG alpha 1, by the isolation of alpha-specific agglutination-defective mutants, followed by isolation of a complementing plasmid. Independently isolated alpha-specific agglutination-defective mutations were in a single complementation group, consistent with biochemical results indicating that the alpha-agglutinin is composed of a single polypeptide. Mapping results suggested that the complementation group identified by these mutants is allelic to the ag alpha 1 mutation identified previously. Expression of AG alpha 1 RNA was alpha specific and inducible by a-factor. Sequences similar to the consensus sequences for positive control by MAT alpha 1 and pheromone induction were found upstream of the AG alpha 1 initiation codon. The AG alpha 1 gene could encode a 650-amino-acid protein with a putative signal sequence, 12 possible N-glycosylation sites, and a high proportion of serine and threonine residues, all of which are features expected for the alpha-agglutinin sequence. Disruption of the AG alpha 1 gene resulted in failure to express alpha-agglutinin and loss of cellular agglutinability in alpha cells. An Escherichia coli fusion protein containing 229 amino acids of the AG alpha 1 sequence was recognized by an anti-alpha-agglutinin antibody. In addition, the ability of this antibody to inhibit agglutination was prevented by this fusion protein. These results indicate that AG alpha 1 encodes alpha-agglutinin. Features of the AG alpha 1 gene product suggest that the amino-terminal half of the protein contains the a-agglutinin binding domain and that the carboxy-terminal half contains a cell surface localization domain, possibly including a glycosyl phosphatidylinositol anchor.
Lipke
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PN
Department of Biological Sciences, Hunter College of the City University of New York, New York 10021.
Wojciechowicz
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D
Kurjan
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J
D000373:Agglutinins / Q000235:genetics*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001483:Base Sequence; D015153:Blotting, Western; D005786:Gene Expression Regulation; D005796:Genes; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D005822:Genetic Vectors; D000072235:Mating Factor; D008562:Membrane Glycoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000235:genetics*; D010675:Pheromones / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development; D012689:Sequence Homology, Nucleic Acid
D000373:Agglutinins; D000596:Amino Acids; D008562:Membrane Glycoproteins; D010455:Peptides; D010675:Pheromones; D000072235:Mating Factor