Prm1p, a pheromone-regulated multispanning membrane protein, facilitates plasma membrane fusion during yeast mating.
Cell fusion occurs throughout development, from fertilization to organogenesis. The molecular mechanisms driving plasma membrane fusion in these processes remain unknown. While yeast mating offers an excellent model system in which to study cell fusion, all genes previously shown to regulate the process act at or before cell wall breakdown; i.e., well before the two plasma membranes have come in contact. Using a new strategy in which genomic data is used to predict which genes may possess a given function, we identified PRM1, a gene that is selectively expressed during mating and that encodes a multispanning transmembrane protein. Prm1p localizes to sites of cell-cell contact where fusion occurs. In matings between Deltaprm1 mutants, a large fraction of cells initiate zygote formation and degrade the cell wall separating mating partners but then fail to fuse. Electron microscopic analysis reveals that the two plasma membranes in these mating pairs are tightly apposed, remaining separated only by a uniform gap of approximately 8 nm. Thus, the phenotype of Deltaprm1 mutants defines a new step in the mating reaction in which membranes are juxtaposed, possibly through a defined adherence junction, yet remain unfused. This phenotype suggests a role for Prm1p in plasma membrane fusion.
Heiman
M G
MG
Howard Hughes Medical Institute and Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California 94143-0448, USA.
Walter
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D000595:Amino Acid Sequence; D001483:Base Sequence; D002459:Cell Fusion; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004171:Diploidy; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects*; D005800:Genes, Fungal / Q000235:genetics / Q000502:physiology; D006238:Haploidy; D008561:Membrane Fusion / Q000187:drug effects; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D010641:Phenotype; D010675:Pheromones / Q000494:pharmacology*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012098:Reproduction / Q000187:drug effects; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D015003:Yeasts / Q000166:cytology* / Q000187:drug effects / Q000235:genetics / Q000254:growth & development
D005656:Fungal Proteins; D008565:Membrane Proteins; C499613:PRM1 protein, S cerevisiae; D010675:Pheromones; D029701:Saccharomyces cerevisiae Proteins