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Amino Acid Sequence
Base Sequence
Biological Transport/physiology
Calcium-Transporting ATPases/analysis/*physiology
Carboxypeptidases/analysis
Cathepsin A
Epitopes
Fungal Proteins/analysis/*metabolism
Genes, Fungal/physiology
Glycosylation
Golgi Apparatus/*chemistry/metabolism
Hot Temperature
Mannose/metabolism
Molecular Sequence Data
Mutation/physiology
Peptides/secretion
Saccharomyces cerevisiae/chemistry/enzymology/*metabolism
Saccharomyces cerevisiae Proteins
Abstract:
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.
