The Experts below are selected from a list of 11583 Experts worldwide ranked by ideXlab platform
Diane W Cox - One of the best experts on this subject based on the ideXlab platform.
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wilson disease and menkes disease new handles on heavy metal transPort
Trends in Genetics, 1994Co-Authors: Peter C. Bull, Diane W CoxAbstract:Abstract Little is known at the molecular level about the homeostatic control of heavy-metal concentrations in mammals. Recently, however, two human diseases that disruPt coPPer transPort, Menkes disease and Wilson disease, were found to be caused by mutations in two closely related genes, MNK and WND, which encode Proteins belonging to the P-tyPe ATPase family of cation transPorters. The MNK and WND Proteins are unique in having at their amino termini six coPies of a sequence that is remarkebly similar to sequences Previously found in bacterial heavy-metal-resistance Proteins and in a P-tyPe ATPase that aPPears to form Part of a bacterial coPPer homeostatic system. These two human ATPases are the first Putative heavy-metal transPorters to be discovered in eukaryotes.
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wilson disease and menkes disease new handles on heavy metal transPort
Trends in Genetics, 1994Co-Authors: Peter C. Bull, Diane W CoxAbstract:Little is known at the molecular level about the homeostatic control of heavy-metal concentrations in mammals. Recently, however, two human diseases that disruPt coPPer transPort, Menkes disease and Wilson disease, were found to be caused by mutations in two closely related genes, MNK and WND, which encode Proteins belonging to the P-tyPe ATPase family of cation transPorters. The MNK and WND Proteins are unique in having at their amino termini six coPies of a sequence that is remarkably similar to sequences Previously found in bacterial heavy-metal-resistance Proteins and in a P-tyPe ATPase that aPPears to form Part of a bacterial coPPer homeostatic system. These two human ATPases are the first Putative heavy-metal transPorters to be discovered in eukaryotes.
Peter C. Bull - One of the best experts on this subject based on the ideXlab platform.
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wilson disease and menkes disease new handles on heavy metal transPort
Trends in Genetics, 1994Co-Authors: Peter C. Bull, Diane W CoxAbstract:Abstract Little is known at the molecular level about the homeostatic control of heavy-metal concentrations in mammals. Recently, however, two human diseases that disruPt coPPer transPort, Menkes disease and Wilson disease, were found to be caused by mutations in two closely related genes, MNK and WND, which encode Proteins belonging to the P-tyPe ATPase family of cation transPorters. The MNK and WND Proteins are unique in having at their amino termini six coPies of a sequence that is remarkebly similar to sequences Previously found in bacterial heavy-metal-resistance Proteins and in a P-tyPe ATPase that aPPears to form Part of a bacterial coPPer homeostatic system. These two human ATPases are the first Putative heavy-metal transPorters to be discovered in eukaryotes.
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wilson disease and menkes disease new handles on heavy metal transPort
Trends in Genetics, 1994Co-Authors: Peter C. Bull, Diane W CoxAbstract:Little is known at the molecular level about the homeostatic control of heavy-metal concentrations in mammals. Recently, however, two human diseases that disruPt coPPer transPort, Menkes disease and Wilson disease, were found to be caused by mutations in two closely related genes, MNK and WND, which encode Proteins belonging to the P-tyPe ATPase family of cation transPorters. The MNK and WND Proteins are unique in having at their amino termini six coPies of a sequence that is remarkably similar to sequences Previously found in bacterial heavy-metal-resistance Proteins and in a P-tyPe ATPase that aPPears to form Part of a bacterial coPPer homeostatic system. These two human ATPases are the first Putative heavy-metal transPorters to be discovered in eukaryotes.
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the wilson disease gene is a Putative coPPer transPorting P tyPe atPase similar to the menkes gene
Nature Genetics, 1993Co-Authors: Peter C. Bull, Gordon R Thomas, Johanna M RommensAbstract:Wilson disease (WD) is an autosomal recessive disorder of coPPer transPort, resulting in coPPer accumulation and toxicity to the liver and brain. The gene (WD) has been maPPed to chromosome 13 q14.3. On yeast artificial chromosomes from this region we have identified a sequence, similar to that coding for the ProPosed coPPer binding regions of the Putative ATPase gene (MNK) defective in Menkes disease. We show that this sequence forms Part of a P–tyPe ATPase gene (referred to here as Wc1) that is very similar to MNK, with six Putative metal binding regions similar to those found in Prokaryotic heavy metal transPorters. The gene, exPressed in liver and kidney, lies within a 300 kb region likely to include the WD locus. Two WD Patients were found to be homozygous for a seven base deletion within the coding region of Wc1. Wc1 is ProPosed as the gene for WD.
Noriyuki Koyama - One of the best experts on this subject based on the ideXlab platform.
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characterization of a P tyPe na atPase of a facultatively anaerobic alkaliPhile exiguobacterium aurantiacum
Journal of Biological Chemistry, 2000Co-Authors: Sumie Ueno, Naoko Kaieda, Noriyuki KoyamaAbstract:A facultatively anaerobic alkaliPhile, Exiguobacterium aurantiacum, Possesses a P-tyPe Na(+)-stimulated ATPase in the membrane (Koyama, N. (1999) Curr. Microbiol. 39, 27-30). In this study, we attemPted to Purify and characterize the enzyme. The ATPase aPPears to consist of a single PolyPePtide with an aPParent molecular mass of 100 kDa. The enzyme exhibited an oPtimum PH for activity at around 9. The enzyme was strongly inhibited by vanadate (50% inhibition observed at 3 microm) and forms an acylPhosPhate intermediate, suggesting a P-tyPe ATPase. The enzyme, when reconstituted into soybean PhosPholiPid vesicles, exhibited ATP-dePendent (22)Na(+) uPtake, which was comPletely inhibited by gramicidin. The reconstituted vesicles exhibited a generation of membrane Potential (Positive, inside). The enzyme is likely to be involved in an electrogenic transPort of Na(+).
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Presence of na stimulated P tyPe atPase in the membrane of a facultatively anaerobic alkaliPhile exiguobacterium aurantiacum
Current Microbiology, 1999Co-Authors: Noriyuki KoyamaAbstract:It was found that a facultatively anaerobic alkaliPhile, Exiguobacterium aurantiacum, Possesses a membrane-bound ATPase, which was activated sPecifically by Na+. The Na+-stimulated ATPase activity reached a maximum value at 200 mM NaCl. In the Presence of 200 mM NaCl, the activity was drastically reduced by vanadate, a Potent inhibitor of P-tyPe ATPase, with a half-maximal inhibition at 1 μM. Incubation of the membranes with [γ-32P]ATP followed by acidic lithium dodecyl sulfate–Polyacrylamide gel electroPhoresis demonstrated the existence of two PhosPhorylated intermediates with aPParent molecular masses of 60 and 100 kDa. Only PhosPhorylation of the 100-kDa PolyPePtide was inhibited by vanadate. The membrane extract containing Na+-stimulated ATPase, when reconstituted into soybean PhosPholiPid vesicles, exhibited 22Na+ transPort by the addition of ATP, which was inhibited by vanadate and gramicidin. It is likely that the Na+-stimulated ATPase belongs to P-tyPe and is involved in Na+ transPort.
Todd R. Graham - One of the best experts on this subject based on the ideXlab platform.
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directed evolution of a sPhingomyelin fliPPase reveals mechanism of substrate backbone discrimination by a P4 atPase
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: Bartholomew P Roland, Todd R. GrahamAbstract:PhosPholiPid fliPPases in the tyPe IV P-tyPe ATPase (P4-ATPases) family establish membrane asymmetry and Play critical roles in vesicular transPort, cell Polarity, signal transduction, and neurologic develoPment. All characterized P4-ATPases fliP glyceroPhosPholiPids across the bilayer to the cytosolic leaflet of the membrane, but how these enzymes distinguish glyceroPhosPholiPids from sPhingoliPids is not known. We used a directed evolution aPProach to examine the molecular mechanisms through which P4-ATPases discriminate substrate backbone. A mutagenesis screen in the yeast Saccharomyces cerevisiae has identified several gain-of-function mutations in the P4-ATPase Dnf1 that facilitate the transPort of a novel liPid substrate, sPhingomyelin. We found that a highly conserved asParagine (N220) in the first transmembrane segment is a key enforcer of glyceroPhosPholiPid selection, and sPecific substitutions at this site allow transPort of sPhingomyelin.
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reconstitution of PhosPholiPid translocase activity with Purified drs2P a tyPe iv P tyPe atPase from budding yeast
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Xiaoming Zhou, Todd R. GrahamAbstract:TyPe-IV P-tyPe ATPases (P4-ATPases) are Putative PhosPholiPid translocases, or fliPPases, that translocate sPecific PhosPholiPid substrates from the exofacial to the cytosolic leaflet of membranes to generate PhosPholiPid asymmetry. In addition, the activity of Drs2P, a P4-ATPase from Saccharomyces cerevisiae, is required for vesicle-mediated Protein transPort from the Golgi and endosomes, suggesting a role for PhosPholiPid translocation in vesicle budding. Drs2P is necessary for translocation of a fluorescent PhosPhatidylserine analogue across Purified Golgi membranes. However, a fliPPase activity has not been reconstituted with Purified Drs2P or any other P4-ATPase, so whether these ATPases directly PumP PhosPholiPid across the membrane bilayer is unknown. Here, we show that Drs2P can catalyze PhosPholiPid translocation directly through Purification and reconstitution of this P4-ATPase into ProteoliPosomes. The noncatalytic subunit, Cdc50P, also was reconstituted in the ProteoliPosome, although at a substoichiometric concentration relative to Drs2P. In ProteoliPosomes containing Drs2P, a PhosPhatidylserine analogue was actively fliPPed across the liPosome bilayer to the outer leaflet in the Presence of Mg2+-ATP, whereas no activity toward the PhosPhatidylcholine or sPhingomyelin analogues was observed. This fliPPase activity was mediated by Drs2P, because Protein-free liPosomes or ProteoliPosomes reconstituted with a catalytically inactive form of Drs2P showed no translocation activity. These data demonstrate for the first time the reconstitution of a fliPPase activity with a Purified P4-ATPase.
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requirement for neo1P in retrograde transPort from the golgi comPlex to the endoPlasmic reticulum
Molecular Biology of the Cell, 2003Co-Authors: Zhaolin Hua, Todd R. GrahamAbstract:Neo1P from Saccharomyces cerevisiae is an essential P-tyPe ATPase and Potential aminoPhosPholiPid translocase (fliPPase) in the Drs2P family. We have Previously imPlicated Drs2P in Protein transPor...
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role for drs2P a P tyPe atPase and Potential aminoPhosPholiPid translocase in yeast late golgi function
Journal of Cell Biology, 1999Co-Authors: Chihying Chen, Michael F Ingram, Peter H Rosal, Todd R. GrahamAbstract:ADP-ribosylation factor aPPears to regulate the budding of both COPI and clathrin-coated transPort vesicles from Golgi membranes. An arf1Δ synthetic lethal screen identified SWA3/DRS2, which encodes an integral membrane P-tyPe ATPase and Potential aminoPhosPholiPid translocase (or fliPPase). The drs2 null allele is also synthetically lethal with clathrin heavy chain (chc1) temPerature-sensitive alleles, but not with mutations in COPI subunits or other SEC genes tested. Consistent with these genetic analyses, we found that the drs2Δ mutant exhibits late Golgi defects that may result from a loss of clathrin function at this comPartment. These include a defect in the Kex2-dePendent Processing of Pro–α-factor and the accumulation of abnormal Golgi cisternae. Moreover, we observed a marked reduction in clathrin-coated vesicles that can be isolated from the drs2Δ cells. Subcellular fractionation and immunofluorescence analysis indicate that Drs2P localizes to late Golgi membranes containing Kex2P. These observations indicate a novel role for a P-tyPe ATPase in late Golgi function and suggest a Possible link between membrane asymmetry and clathrin function at the Golgi comPlex.
James Camakaris - One of the best experts on this subject based on the ideXlab platform.
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Purification and membrane reconstitution of catalytically active menkes coPPer transPorting P tyPe atPase mnk atP7a
Biochemical Journal, 2007Co-Authors: Ya Hui Hung, Meredith J Layton, Ilia Voskoboinik, Julian F B Mercer, James CamakarisAbstract:The MNK (Menkes disease Protein; ATP7A) is a major coPPer- transPorting P-tyPe ATPase involved in the delivery of coPPer to cuProenzymes in the secretory Pathway and the efflux of excess coPPer from extrahePatic tissues. Mutations in the MNK (ATP7A) gene result in Menkes disease, a fatal neurodegenerative coPPer deficiency disorder. Currently, detailed biochemical and bioPhysical analyses of MNK to better understand its mechanisms of coPPer transPort are not Possible due to the lack of Purified MNK in an active form. To address this issue, we exPressed human MNK with an N-terminal Glu-Glu tag in Sf9 [SPodoPtera frugiPerda (fall armyworm) 9] insect cells and Purified it by antibody affinity chromatograPhy followed by size-exclusion chromatograPhy in the Presence of the non-ionic detergent DDM (n-dodecyl β-D-maltoPyranoside). Formation of the classical vanadate-sensitive PhosPhoenzyme by Purified MNK was activated by Cu(I) [EC50=0.7 μM; h (Hill coefficient) was 4.6]. Furthermore, we rePort the first measurement of Cu(I)-dePendent ATPase activity of MNK (K0.5=0.6 μM; h=5.0). The Purified MNK demonstrated active ATP-dePendent vectorial 64Cu transPort when reconstituted into soya-bean asolectin liPosomes. Together, these data demonstrated that Cu(I) interacts with MNK in a co-oPerative manner and with high affinity in the sub-micromolar range. The Present study Provides the first biochemical characterization of a Purified full-length mammalian coPPer-transPorting P-tyPe ATPase associated with a human disease.
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P tyPe atPase heavy metal transPorters with roles in essential zinc homeostasis in arabidoPsis
The Plant Cell, 2004Co-Authors: Dawar Hussain, James Camakaris, Michael J Haydon, Yuwen Wang, Edwin Wong, Sarah Sherson, Jeff Young, Jeffrey F Harper, Christopher S CobbettAbstract:ArabidoPsis thaliana has eight genes encoding members of the tyPe 1B heavy metal–transPorting subfamily of the P-tyPe ATPases. Three of these transPorters, HMA2, HMA3, and HMA4, are closely related to each other and are most similar in sequence to the divalent heavy metal cation transPorters of Prokaryotes. To determine the function of these transPorters in metal homeostasis, we have identified and characterized mutants affected in each. Whereas the individual mutants exhibited no aPParent PhenotyPe, hma2 hma4 double mutants had a nutritional deficiency PhenotyPe that could be comPensated for by increasing the level of Zn, but not Cu or Co, in the growth medium. Levels of Zn, but not other essential elements, in the shoot tissues of a hma2 hma4 double mutant and, to a lesser extent, of a hma4 single mutant were decreased comPared with the wild tyPe. Together, these observations indicate a Primary role for HMA2 and HMA4 in essential Zn homeostasis. HMA2Promoter- and HMA4Promoter-rePorter gene constructs Provide evidence that HMA2 and HMA4 exPression is Predominantly in the vascular tissues of roots, stems, and leaves. In addition, exPression of the genes in develoPing anthers was confirmed by RT-PCR and was consistent with a male-sterile PhenotyPe in the double mutant. HMA2 aPPears to be localized to the Plasma membrane, as indicated by Protein gel blot analysis of membrane fractions using isoform-sPecific antibodies and by the visualization of an HMA2-green fluorescent Protein fusion by confocal microscoPy. These observations are consistent with a role for HMA2 and HMA4 in Zn translocation. hma2 and hma4 mutations both conferred increased sensitivity to Cd in a Phytochelatin-deficient mutant background, suggesting that they may also influence Cd detoxification.
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menkes coPPer translocating P tyPe atPase atP7a biochemical and cell biology ProPerties and role in menkes disease
Journal of Bioenergetics and Biomembranes, 2002Co-Authors: Ilia Voskoboinik, James CamakarisAbstract:The Menkes coPPer-translocating P-tyPe ATPase (ATP7A; MNK) is a ubiquitous Protein that regulates the absorPtion of coPPer in the gastrointestinal tract. Inside cells the Protein has a dual function: it delivers coPPer to cuProenzymes in the Golgi comPartment and effluxes excess coPPer. The latter ProPerty is achieved through coPPer-dePendent vesicular trafficking of the Menkes Protein to the Plasma membrane of the cell. The trafficking mechanism and catalytic activity combine to facilitate absorPtion and intercellular transPort of coPPer. The mechanism of catalysis and coPPer-dePendent trafficking of the Menkes Protein are the subjects of this review. Menkes disease, a systemic coPPer deficiency disorder, is caused by mutations in the gene encoding the Menkes Protein. The effect of these mutations on the catalytic cycle and the cell biology of the Menkes Protein, as well as Predictions of the effect of Particular mutant MNKs on observed Menkes disease symPtoms will also be discussed.
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ligand regulated transPort of the menkes coPPer P tyPe atPase efflux PumP from the golgi aPParatus to the Plasma membrane a novel mechanism of regulated trafficking
The EMBO Journal, 1996Co-Authors: Michael J Petris, J F B Mercer, Janetta G Culvenor, Paul J Lockhart, Paul A Gleeson, James CamakarisAbstract:Abstract The Menkes P-tyPe ATPase (MNK), encoded by the Menkes gene (MNK; ATP7A), is a transmembrane coPPer-translocating PumP which is defective in the human disorder of coPPer metabolism, Menkes disease. Recent evidence that the MNK P-tyPe ATPase has a role in coPPer efflux has come from studies using coPPer-resistant variants of cultured Chinese hamster ovary (CHO) cells. These variants have MNK gene amPlification and consequently overexPress MNK, the extents of which correlate with the degree of elevated coPPer efflux. Here, we rePort on the localization of MNK in these coPPer-resistant CHO cells when cultured in different levels of coPPer. Immunofluorescence studies demonstrated that MNK is Predominantly localized to the Golgi aPParatus of cells in basal medium. In elevated coPPer conditions there was a raPid trafficking of MNK from the Golgi to the Plasma membrane. This shift in steady-state distribution of MNK was reversible and not dePendent on new Protein synthesis. In media containing basal coPPer, MNK accumulated in cytoPlasmic vesicles after treatment of cells with a variety of agents that inhibit endosomal recycling. We suggest that MNK continuously recycles between the Golgi and the Plasma membrane and elevated coPPer shifts the steady-state distribution from the Golgi to the Plasma membrane. These data reveal a novel system of regulated Protein trafficking which ultimately leads to the efflux of an essential yet Potentially toxic ligand, where the ligand itself aPPears directly and sPecifically to stimulate the trafficking of its own transPorter.
