A novel protein, CSG2p, is required for Ca2+ regulation in Saccharomyces cerevisiae.
Nineteen mutants that lost the ability to grow in 100 mM Ca2+ (but remained insensitive to 50 mM Sr2+) were identified in a screen of approximately 60,000 mutagenized yeast colonies. Cells carrying mutations in the CSG2 gene grow normally in low Ca2+ medium but have decreased growth rates when the Ca2+ concentration is above 10 mM. The csg2 mutant cells accumulate much higher levels of Ca2+ in a compartment that is exchangeable with extracellular Ca2+ but the nonexchangeable Ca2+ pool which predominates in wild-type cells is not influenced. Sr2+ influx is not increased in the csg2 mutant cells. Mg2+ decreases the amount of Ca2+ in the non-exchangeable pool without influencing the csg2-induced exchangeable Ca2+ pool. The data indicate that the csg2 mutation causes a selective increase in Ca2+ accumulation into a pool which is distinct from the vacuolar pool. The CSG2 protein consists of 410 amino acids, contains nine putative transmembrane segments, four potential sites for N-linked glycosylation, and a sequence with homology to the EF-hand Ca(2+)-binding site.
Beeler
T
T
Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814.
Gable
K
K
Zhao
C
C
Dunn
T
T
D000595:Amino Acid Sequence; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002874:Chromosome Mapping; D015825:Chromosomes, Fungal; D003001:Cloning, Molecular; D004271:DNA, Fungal; D004926:Escherichia coli; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins
C086192:CSG2 protein, S cerevisiae; D002135:Calcium-Binding Proteins; D004271:DNA, Fungal; D005656:Fungal Proteins; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; D002118:Calcium