Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tonoplast vesicles were isolated by discontinuous sucrose gradient centrifugation in the presence of Mg(2+) from 5 day old corn (Zea mays L., Golden Cross Bantam) seedling roots. Marker enzyme assays indicated only a low degree of cross-contamination of tonoplast vesicles at the 10/23% (weight/weight) interface by other membrane components. Severalfold enrichment of tonoplast ATPase and pyrophosphatase was indicated in tonoplast fractions by dot blot studies with antibodies against an oat tonoplast ATPase and a mung bean tonoplast pyrophosphatase. Comparison of two-dimensional electrophoretic gels of tonoplast and microsomal membrane polypeptides revealed approximately 68 polypeptides to be specific to tonoplast by silver staining. Immunoblot analysis with antibodies against a tonoplast holoenzyme ATPase from oat roots revealed the presence of the 72, 60, and 41 kilodalton polypeptides in isolated tonoplast vesicles from corn roots. Affinity blotting with concanavalin A and secondary antibodies indicated the degree of glycosylation of tonoplast polypeptides, where 21 of 68 tonoplast-specific polypeptides contained detectable carbohydrate moieties. Salt and NaOH washes removed 38 of the tonoplast-specific polypeptides, indicating a peripheral association with the membrane. Thirteen of the peripheral polypeptides and eight of the integral polypeptides were identified as glycoproteins. This information on the polypeptide composition of the tonoplast of root cells will aid in gaining insight into the role of this membrane in controlling vacuolar functions.
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PMID:Characterization of tonoplast polypeptides isolated from corn seedling roots. 1666 81

We investigated the involvement of angiotensin II and vascular smooth muscle sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) function in the impaired NO-induced relaxation seen in established streptozotocin-induced diabetes. Plasma angiotensin II levels, which were elevated in untreated diabetic rats (vs age-matched controls), were improved by treatment with the angiotensin-converting enzyme inhibitor enalapril. Systolic blood pressure was significantly decreased in chronic enalapril-treated diabetics (vs the other two groups). Intact aortae from diabetic rats and chronic angiotensin II-infused control rats, but not those from diabetic rats treated with enalapril, showed impaired endothelium-dependent relaxations to acetylcholine (vs controls). The relaxation induced by Angeli's Salt (a NO donor) was significantly impaired in endothelium-denuded aortae from diabetic rats (vs controls) but it was normalised by enalapril treatment. After preincubation with the irreversible SERCA inhibitor, thapsigargin, the relaxation induced by Angeli's Salt was significantly impaired in endothelium-denuded aortae from the controls, but not from the diabetics, and there was no significant difference between the thapsigargin-treated groups. Nitrotyrosine, an indirect marker of peroxynitrite, was markedly increased in aortic smooth muscle from diabetic rats, while chronic enalapril administration reduced this increase. These results suggest that in streptozotocin-induced diabetic rats, excessive angiotensin II production may lead to the generation of peroxynitrite and that this may in turn trigger a dysfunction of vascular smooth muscle SERCA. Enalapril improved the diabetes-related impairments.
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PMID:Enalapril improves impairment of SERCA-derived relaxation and enhancement of tyrosine nitration in diabetic rat aorta. 1719 60

Changes in myocardial expression of Na+/K+-ATPase alpha-subunit isoforms have been demonstrated in different models of cardiac hypertrophy and hypertension. Here we studied the expression of these isozymes in stroke-prone spontaneously hypertensive rats (SHRSP) and the influence of high salt diet and treatment with the dihydropyridine lacidipine. Adult SHRSP were offered either 1% NaCl or water as drinking solution for 6 weeks. Salt-loaded SHRSP were treated or not with 1 mg/kg/day lacidipine. Compared to Wistar Kyoto (WKY) rats, non-salt-loaded SHRSP presented significant hypertension and cardiac hypertrophy. Salt intake markedly enhanced cardiac hypertrophy, an effect blunted by lacidipine. [3H]Ouabain binding assays on total particulate fractions from heart ventricles revealed the existence of two high-affinity sites with Kd approximately 25 and approximately 200 nM, ascribed to the alpha3 and alpha2 isoforms, respectively. Bmax of alpha3 was unexpectedly high (40% of total high-affinity binding) in ventricles from WKY rats but very low in all groups of SHRSP. On the other hand, Bmax of alpha2 was similar in WKY and non-salt-loaded SHRSP; however, salt loading of SHRSP resulted in a Bmax reduction of 20% (P<0.05), an effect blocked by lacidipine. These effects were largely confirmed by immunoblotting analysis, which, in addition, demonstrated that the density of the ubiquitous alpha1 isoform was comparable among the experimental groups. In conclusion, WKY rats showed a high myocardial expression of the Na+/K+-ATPase alpha3 subunit, which was not found in SHRSP; the level of the alpha2 isoform was similar in untreated SHRSP and WKY; salt-loading of SHRSP promoted reduction of the alpha2 isoform, and this effect was completely hampered by lacidipine.
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PMID:Na+/K+-ATPase alpha isoforms expression in stroke-prone spontaneously hypertensive rat heart ventricles: effect of salt loading and lacidipine treatment. 1745 77

Citrate-mediated iron transport across the cytoplasmic membrane is catalyzed by an ABC transporter that consists of the periplasmic binding protein FecB, the transmembrane proteins FecC and FecD, and the ATPase FecE. Salt bridges between glutamate residues of the binding protein and arginine residues of the transmembrane proteins are predicted to mediate the positioning of the substrate-loaded binding protein on the transmembrane protein, based on the crystal structures of the ABC transporter for vitamin B(12), consisting of the BtuF binding protein and the BtuCD transmembrane proteins (E. L. Borths et al., Proc. Natl. Acad. Sci. USA 99:16642-16647, 2002). Here, we examined the role of the residues predicted to be involved in salt-bridge formation between FecB and FecCD by substituting these residues with alanine, cysteine, arginine, and glutamate and by analyzing the citrate-mediated iron transport of the mutants. Replacement of E93 in FecB with alanine [FecB(E93A)], cysteine, or arginine nearly abolished citrate-mediated iron transport. Mutation FecB(E222R) nearly eliminated transport, and FecB(E222A) and FecB(E222C) strongly reduced transport. FecD(R54C) and FecD(R51E) abolished transport, whereas other R-to-C mutations in putative interaction sites between FecCD and FecB substantially reduced transport. The introduced cysteine residues in FecB and FecCD also served to examine the formation of disulfide bridges in place of salt bridges between the binding protein and the transmembrane proteins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis results suggest cross-linking of FecB(E93C) to FecD(R54C) and FecB(E222C) to FecC(R60C). The data are consistent with the proposal that FecB(E93) is contained in the region that binds to FecD and FecB(E222) in the region that binds to FecC.
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PMID:Docking of the periplasmic FecB binding protein to the FecCD transmembrane proteins in the ferric citrate transport system of Escherichia coli. 1766 Feb 86

The brine shrimp Artemia thrives at extreme conditions of up to 300 g/l salt in hypersaline lakes, but the molecular aspects of this salt adaptation are not clarified. To examine the influence of salt on the expression of two isoforms of Na,K-ATPase, adult Artemia franciscana were cultured for 39 days with the microalga Dunaliella salina as fodder at increasing salt from 30 to 280 g/l. Quantitative reverse-transcriptase polymerase chain reaction showed that the abundance of mRNA of the lysine-substituted alpha(2)(KK)-subunit was very low at 30 g/l salt but rose steeply in the range of 70-200 g/l to a level at 200-280 g/l salt, similar to the abundance of the mRNA of the alpha(1)(NN)-subunit, which was insignificantly affected by increasing salt. Site-directed mutagenesis showed that Asn324Lys and Asn776Lys in the alpha(1)-subunit of pig kidney Na,K-ATPase reduced the stoichiometry of (204)Tl binding from 2 to about 1 Tl(+)(K(+)) per alpha-subunit and Na(+)-dependent phosphorylation from ATP to 25-30%. In structure models, the epsilon-amino group of Lys776 is located at cation site 1 in the E(1)P form and near cation site 2 in the E(2) conformation, while the side chain of Lys324 points away from the cation sites. Salt-induced expression of the alpha(2)(KK)-subunit Na,K-ATPase in A. franciscana may reduce the Na(+)/ATP ratio and enable the Na,K pump to extrude Na(+) against steeper gradients and, thus, contribute to salt adaptation.
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PMID:Regulation and function of lysine-substituted Na,K pumps in salt adaptation of Artemia franciscana. 1807 67

RAD51 and other members of the RecA family of strand exchange proteins assemble on ssDNA to form presynaptic filaments, which carry out the central steps of homologous recombination. A microplate-based assay was developed for high-throughput measurement of hRAD51 filament formation on ssDNA. With this method, a 10,000 compound library was screened, leading to the identification of a small molecule (RS-1) that enhances hRAD51 binding in a wide range of biochemical conditions. Salt titration experiments showed that RS-1 can enhance filament stability. Ultrastructural analysis of filaments formed on ssDNA showed that RS-1 can increase both protein-DNA complex lengths and the pitch of helical filament turns. RS-1 stimulated hRAD51-mediated homologous strand assimilation (D-loop) activity by at least 5- to 11-fold, depending on the condition. This D-loop stimulation occurred even in the presence of Ca(2+) or adenylyl-imidodiphosphate, indicating that the mechanism of stimulation was distinct from that conferred by Ca(2+) and/or inhibition of ATPase. No D-loop activity was observed in the absence of a nucleotide triphosphate cofactor, indicating that the compound does not substitute for this requirement. These results indicate that RS-1 enhances the homologous recombination activity of hRAD51 by promoting the formation of active presynaptic filaments. Cell survival assays in normal neonatal human dermal fibroblasts demonstrated that RS-1 promotes a dose-dependent resistance to the cross-linking chemotherapeutic drug cisplatin. Given that RAD51-dependent recombination is a major determinant of cisplatin resistance, RS-1 seems to function in vivo to stimulate homologous recombination repair proficiency. RS-1 has many potential applications in both research and medical settings.
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PMID:A chemical compound that stimulates the human homologous recombination protein RAD51. 1884 Jun 82

We report an analysis of salt-stress responses in the monocotyledonous halophyte Festuca rubra ssp. litoralis. Salt-dependent expression of transcripts encoding a PIP2;1 aquaporin, V-ATPase subunit B, and the Na+/H+ antiporter NHX was characterized. Transcription of FrPIP2;1, FrVHA-B, and FrNHX1 was induced in root tissue of F. rubra ssp. litoralis by salt treatment, and during salt-stress F. rubra ssp. litoralis accumulated sodium in leaves and roots. Cell specificity of FrPIP2;1, FrVHA-B, and FrNHX1 transcription was analyzed by in situ PCR in roots of F. rubra ssp. litoralis. Expression of the genes was localized to the root epidermis, cortex cells, endodermis, and the vascular tissue. In plants treated with 500 mM NaCl, transcripts were repressed in the epidermis and the outer cortex cells, whereas endodermis and vasculature showed strong signals. These data demonstrate that transcriptional regulation of the aquaporin PIP2;1, V-ATPase, and the Na+/H+ antiporter NHX is correlated with salt tolerance in F. rubra ssp. litoralis and suggests coordinated control of ion homeostasis and water status at high salinity in plants. Salt-induced transcript accumulation in F. rubra ssp. litoralis was further monitored by cDNA-arrays with expressed sequence tags derived from a cDNA subtraction library. The salt-regulated transcripts included those involved in the control of gene expression and signal transduction elements such as a serine/threonine protein kinase, an SNF1-related protein kinase, and a WRKY-type transcription factor. Other ESTs with salt-dependent regulation included transcripts encoding proteins that function in metabolism, general stress responses, and defense and transport proteins.
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PMID:Transcript profiling of the salt-tolerant Festuca rubra ssp. litoralis reveals a regulatory network controlling salt acclimatization. 1981 29

Using the non-invasively ion-selective microelectrode technique, flux profiles of K(+), Na(+) and H(+) in mature roots and apical regions, and the effects of Ca(2+) on ion fluxes were investigated in salt-tolerant poplar species, Populus euphratica Oliver and salt-sensitive Populus simonii x (P. pyramidalis + Salix matsudana) (Populus popularis 35-44, P. popularis). Compared to P. popularis, P. euphratica roots exhibited a greater capacity to retain K(+) after exposure to a salt shock (SS, 100 mM NaCl) and a long-term (LT) salinity (50 mM NaCl, 3 weeks). Salt shock-induced K(+) efflux in the two species was markedly restricted by K(+) channel blocker, tetraethylammonium chloride, but enhanced by sodium orthovanadate, the inhibitor of plasma membrane (PM) H(+)-ATPase, suggesting that the K(+) efflux is mediated by depolarization-activated (DA) channels, e.g., KORCs (outward rectifying K(+) channels) and NSCCs (non-selective cation channels). Populus euphratica roots were more effective to exclude Na(+) than P. popularis in an LT experiment, resulting from the Na(+)/H(+) antiport across the PM. Moreover, pharmacological evidence implies that the greater ability to control K(+)/Na(+) homeostasis in salinized P. euphratica roots is associated with the higher H(+)-pumping activity, which provides an electrochemical H(+) gradient for Na(+)/H(+) exchange and simultaneously decreases the NaCl-induced depolarization of PM, thus reducing Na(+) influx via NSCCs and K(+) efflux through DA-KORCs and DA-NSCCs. Ca(2+) application markedly limited salt-induced K(+) efflux but enhanced the apparent Na(+) efflux, thus enabling the two species, especially the salt-sensitive poplar, to retain K(+)/Na(+) homeostasis in roots exposed to prolonged NaCl treatment.
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PMID:Calcium mediates root K+/Na+ homeostasis in poplar species differing in salt tolerance. 1963 60

Although barley (Hordeum vulgare L.) is a salt-tolerant crop, the underlying physiological and molecular mechanisms of salt tolerance remain to be elucidated. Therefore, we investigated the response of salt-tolerant (K305) and salt-sensitive (I743) cultivars to salt stress at both physiological and molecular levels. Salt treatment increased xylem sap osmolarity, which was attributed primarily to a rise in Na(+) and Cl(-) concentration; enhanced accumulation of the ions in shoots; and reduced plant growth more severely in I743 than K305. The concentration of K(+) in roots and shoots decreased during 8 h of salt treatment in both cultivars but with no marked difference between cultivars. Hence, the severe growth reduction in I743 is attributed to the elevated levels of (mainly) Na(+) in shoots. Analysis of gene expression using quantitative RT-PCR showed that transcripts of K(+)-transporters (HvHAK1 and HvAKT1), vacuolar H(+)-ATPase and inorganic pyrophosphatase (HvHVA/68 and HvHVP1) were more abundant in shoots of K305 than in shoots of I743. Expression of HvHAK1 and Na(+)/H(+) antiporters (HvNHX1, HvNHX3 and HvNHX4) was higher in roots of K305 than in I743 with prolonged exposure to salt. Taken together, these results suggest that the better performance of K305 compared to I743 during salt stress may be related to its greater ability to sequester Na(+) into sub-cellular compartments and/or maintain K(+) homeostasis.
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PMID:Insights into the salt tolerance mechanism in barley (Hordeum vulgare) from comparisons of cultivars that differ in salt sensitivity. 1990 21

The renal proximal tubule (RPT) is a central locale for Na+ reabsorption, and blood pressure regulation. Na+ reabsorption in the RPT depends upon the Na,K-ATPase, which is controlled by a complex regulatory network, including Salt-Inducible Protein Kinase (SIK). SIKs are recently discovered members of the AMP-activated Protein Kinase (AMPK) family, which regulate salt homeostasis and metabolism in a number of tissues. In the RPT, SIK interacts with the Na,K-ATPase in the basolateral membrane (BM), regulating both the activity and level of Na,K-ATPase in the BM. Thus, Na,K-ATPase activity can be rapidly adjusted in response to changes in Na+ balance. Long-term changes in Na+ intake affect the state of SIK phosphorylation, and as a consequence the phosphorylation of TORCs, Transducers of Regulated CREB (cAMP Regulatory Element Binding Protein). Once phosphorylated, TORCs enter the nucleus, and activate transcription of the ATP1B1 gene encoding for the Na,K-ATPase beta subunit.
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PMID:Targeting of renal proximal tubule Na,K-ATPase by salt-inducible kinase. 2015 10


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