spf1p

P5-ATPases are important for processes associated with the endosomal-lysosomal system of eukaryotic cells. In humans, the loss of function of P5-ATPases causes neurodegeneration. In the yeastSaccharomyces cerevisiae, deletion of P5-ATPase Spf1p gives rise to endoplasmic reticulum stress. The reaction cycle of P5-ATPases is poorly characterized. Here, we showed that the formation of the Spf1p catalytic phosphoenzyme was fast in a reaction medium containing ATP, Mg(2+), and EGTA. Low concentrations of Ca(2+)in the phosphorylation medium decreased the rate of phosphorylation and the maximal level of phosphoenzyme...

BACKGROUND: P-type ATPases are ubiquitous ion and lipid pumps found in cellular membranes. P5A-ATPases constitute a poorly characterized subfamily of P-type ATPases present in all eukaryotic organisms but for which a transported substrate remains to be identified. SCOPE OF REVIEW: This review aims to discuss the available evidence which could lead to identification of possible substrates of P5A-ATPases. MAJOR CONCLUSIONS: The complex phenotypes resulting from the loss of P5A-ATPases in model organisms can be explained by a role of the P5A-ATPase in the endoplasmic reticulum (ER), where loss of function leads to broad and unspecific phenotypes related to the impairment of basic ER functions such as protein folding and processing...

The endoplasmic reticulum (ER) is a large, multifunctional and essential organelle. Despite intense research, the function of more than a third of ER proteins remains unknown even in the well-studied model organism Saccharomyces cerevisiae. One such protein is Spf1, which is a highly conserved, ER localized, putative P-type ATPase. Deletion of SPF1 causes a wide variety of phenotypes including severe ER stress suggesting that this protein is essential for the normal function of the ER. The closest homologue of Spf1 is the vacuolar P-type ATPase Ypk9 that influences Mn(2+) homeostasis...

Spf1p is a P-type ATPase that is mainly localized to the endoplasmic reticulum (ER) in Saccharomyces cerevisiae. The protein is involved in the maintenance of ion homeostasis in the ER. To investigate the intracellular role of Spf1p in more detail, we performed a genetic screen for mutations that lead to synthetic lethality in combination with a disruption of SPF1; the mutations identified have been termed lws (for lethal with spf1) mutations. Mutant alleles of five LWS genes (MDM39, RIC1, LAS21, TUP1 and BTS1) were recovered...

The internal environment of the ER is regulated to accommodate essential cellular processes, yet our understanding of this regulation remains incomplete. Cod1p/Spf1p belongs to the widely conserved, uncharacterized type V branch of P-type ATPases, a large family of ion pumps. Our previous work suggested Cod1p may function in the ER. Consistent with this hypothesis, we localized Cod1p to the ER membrane. The cod1Delta mutant disrupted cellular calcium homeostasis, causing increased transcription of calcium-regulated genes and a synergistic increase in cellular calcium when paired with disruption of the Golgi apparatus-localized Ca2+ pump Pmr1p...

Yeast protein insertion orientation (PIO) mutants were isolated by selecting for growth on sucrose in cells in which the only source of invertase is a C-terminal fusion to a transmembrane protein. Only the fraction with an exocellular C terminus can be processed to secreted invertase and this fraction is constrained to 2-3% by a strong charge difference signal. Identified pio mutants increased this to 9-12%. PIO1 is SPF1, encoding a P-type ATPase located in the endoplasmic reticulum (ER) or Golgi. spf1-null mutants are modestly sensitive to EGTA...

The yeast SPF1 gene encodes a novel P-type ATPase, the substrate of which specificity has not been identified. It is required for sensitivity to SMKT, a killer toxin produced by the halotolerant yeast Pichia farinosa. To investigate the function of Spf1p, Asp487, the putative phosphorylation site of Spf1p, was replaced by Asn. Expression of the altered SPF1, with Asp487 replaced by Asn, did not suppress the SMKT-resistant phenotype of spf1 mutants, suggesting that the catalytic activity of this ATPase is required for acquisition of sensitivity to SMKT...

The integral ER membrane protein HMG-CoA reductase (HMGR) is a key enzyme of the mevalonate pathway from which sterols and other essential molecules are produced. HMGR degradation occurs in the ER and is regulated by mevalonate-derived signals. Little is known about the mechanisms responsible for regulating HMGR degradation. The yeast Hmg2p isozyme of HMGR undergoes regulated degradation in a manner very similar to mammalian HMGR, allowing us to isolate mutants deficient in regulating Hmg2p stability. We call these mutants cod mutants for the control of HMG-CoA reductase degradation...