The yeast Ca(2+)-ATPase homologue, PMR1, is required for normal Golgi function and localizes in a novel Golgi-like distribution.
PMR1, a Ca(2+)-adenosine triphosphatase (ATPase) homologue in the yeast Saccharomyces cerevisiae localizes to a novel Golgi-like organelle. Consistent with a Golgi localization, the bulk of PMR1 comigrates with Golgi markers in subcellular fractionation experiments, and staining of PMR1 by indirect immunofluorescence reveals a punctate pattern resembling Golgi staining in yeast. However, PMR1 shows only partial colocalization with known Golgi markers, KEX2 and SEC7, in double-label immunofluorescence experiments. The effect of PMR1 on Golgi function is indicated by pleiotropic defects in various Golgi processes in pmr1 mutants, including impaired proteolytic processing of pro-alpha factor and incomplete outer chain glycosylation of invertase. Consistent with the proposed role of PMR1 as a Ca2+ pump, these defects are reversed by the addition of millimolar levels of extracellular Ca2+, suggesting that Ca2+ disposition is essential to normal Golgi function. Absence of PMR1 function partially suppresses the temperature-sensitive growth defects of several sec mutants, and overexpression of PMR1 restricts the growth of others. Some of these interactions are modulated by changes in external Ca2+ concentrations. These results imply a global role for Ca2+ in the proper function of components governing transit and processing through the secretory pathway.
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Whitehead Institute of Biomedical Research, Cambridge, Massachusetts.
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D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000032:analysis / Q000502:physiology*; D002268:Carboxypeptidases / Q000032:analysis; D043402:Cathepsin A; D000939:Epitopes; D005656:Fungal Proteins / Q000032:analysis / Q000378:metabolism*; D005800:Genes, Fungal / Q000502:physiology; D006031:Glycosylation; D006056:Golgi Apparatus / Q000737:chemistry* / Q000378:metabolism; D006358:Hot Temperature; D008358:Mannose / Q000378:metabolism; D000072235:Mating Factor; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology; D010455:Peptides / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins
D000939:Epitopes; D005656:Fungal Proteins; D010455:Peptides; D029701:Saccharomyces cerevisiae Proteins; D000072235:Mating Factor; D002268:Carboxypeptidases; D043402:Cathepsin A; C499283:PRC1 protein, S cerevisiae; C022633:serine carboxypeptidase; D000252:Calcium-Transporting ATPases; D008358:Mannose