title: Study of a temperature-sensitive mutant of the ras-related YPT1 gene product in yeast suggests a role in the regulation of intracellular calcium.
abstract: Intragenic mutations were isolated that suppressed the dominant-lethal phenotype of the YPT1ile121 mutant gene in a temperature-dependent fashion. Among different amino acid substitutions resulting from single point mutations, two, Ala161----Val (A161V) and Met165----Ile (M165I), restored the function of the YPT1ile121 mutant protein. Mutants expressing the YPT1ile121/val161 allele (ypt1ts) only, grew normally at temperatures up to 30 degrees C but were arrested at 37 degrees C. At the restrictive temperature, ypt1ts mutants accumulated ER membranes, small vesicles, and unprocessed invertase, and they exhibited cytoskeletal defects and an enhanced 45Ca2+ uptake. Similar alterations were seen in YPT1-depleted cells. The ypt1ts mutant cells could be rescued from growth arrest by increasing extracellular Ca2+, and, even at the permissive temperature, they displayed increased trifluoperazine sensitivity.
authors.affiliation: Max Planck Institute for Biophysical Chemistry, Department of Molecular Genetics, Göttingen, Federal Republic of Germany.
authors.forename: H D
authors.initials: HD
authors.lastname: Schmitt
authors.forename: M
authors.initials: M
authors.lastname: Puzicha
authors.forename: D
authors.initials: D
authors.lastname: Gallwitz
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics*; D005786:Gene Expression Regulation; D005800:Genes, Fungal; D011905:Genes, ras; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D013489:Suppression, Genetic; D013696:Temperature; D018631:ras Proteins
chemical_list: D005656:Fungal Proteins; D018631:ras Proteins; D002118:Calcium