Multiple functions of the vacuolar sorting protein Ccz1p in Saccharomyces cerevisiae.
The CCZ1 (YBR131w) gene encodes a protein required for fusion of various transport intermediates with the vacuole. Ccz1p, in a complex with Mon1p, is a close partner of Ypt7p in the processes of fusion of endosomes to vacuoles and homotypic vacuole fusion. In this work, we exploited the Ca(2+)-sensitivity of the ccz1Delta mutant to identify genes specifically interacting with CCZ1, basing on functional multicopy suppression of calcium toxicity. The presented results indicate that Ccz1p functions in the cell either in association with Mon1p and Ypt7p in fusion at the vacuolar membrane, or--separately--with Arl1p at early steps of vacuolar transport. We also show that suppression of calcium toxicity by the calcium pumps Pmr1p and Pmc1p is restricted only to the subset of mutants defective in vacuole morphology. The mechanisms of Ca(2+)-pump-mediated suppression also differ from each other, since the action of Pmr1p, but not Pmc1p, appears to require Arl1p function.
Hoffman-Sommer
Marta
M
Institute of Biochemistry and Biophysics PAS, Pawinskiego 5A, 02-106 Warsaw, Poland.
Migdalski
Andrzej
A
Rytka
Joanna
J
Kucharczyk
Róza
R
D002118:Calcium / Q000378:metabolism; D049109:Cell Proliferation; D004247:DNA / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism / Q000502:physiology*; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology*; D013696:Temperature; D014617:Vacuoles / Q000737:chemistry / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism / Q000502:physiology*; D020691:rab GTP-Binding Proteins / Q000378:metabolism
C441960:Ccz1 protein, S cerevisiae; D020662:Guanine Nucleotide Exchange Factors; C470635:Mon1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D004247:DNA; C487039:ARL1 protein, S cerevisiae; C079005:YPT7 protein, S cerevisiae; D020559:Monomeric GTP-Binding Proteins; D020691:rab GTP-Binding Proteins; D002118:Calcium