Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the present report we describe a method for purifying plasma membranes from chicken erythrocytes using sonication under conditions that facilitate preferential lysis of plasma membrane, followed by centrifugation through a sucrose gradient. The Ca(2+)-dependent ATP hydrolysis by plasma membranes is activated by nanomolar levels of calmodulin, similarly to that from anucleated erythrocytes. Inside-out vesicles display a calmodulin-activated Ca2+ uptake. Purified Ca(2+)-ATPase is obtained from the plasma membrane by Sepharose-calmodulin affinity chromatography, and exhibits an apparent molecular mass of 150 kDa on SDS-polyacrylamide gel electrophoresis, clearly showing that the enzyme is distinct from that described in anucleated erythrocytes (140 kDa). The enzyme is insensitive to physiological concentrations of taurine, a beta-amino acid that has been proposed to be involved in Ca2+ homeostasis of nucleated erythrocytes, suggesting that the effect of taurine is not mediated by the Ca(2+)-ATPase. Taken together, these data suggest that the enzyme may be an isoform that resembles the previously described plasma membrane Ca(2+)-ATPase from anucleated erythrocytes in its regulation by calmodulin, but differs in its apparent molecular weight.
Comp Biochem Physiol B Biochem Mol Biol 1999 Mar
PMID:Ca(2+)-ATPase from chicken (Gallus domesticus) erythrocyte plasma membrane: effects of calmodulin and taurine on the Ca(2+)-dependent ATPase activity and Ca2+ uptake. 1037 56

The tomato LCA1 gene encodes a Ca2+-ATPase and gives rise to two major mRNA transcripts and two distinct protein products of different size in tomato roots. The basis of the transcript size difference was investigated to assess whether the mRNA transcripts encoded distinct protein products. Primer extension and S1 nuclease analysis identified two transcription initiation sites at -72 and -1392 from the start of translation. RNA gel blot analysis of poly(A)+ RNA isolated from phosphate-starved tomato roots using probes designed to domains of the 5'-untranslated region (UTR) or the full-length LCA1 cDNA identified mRNAs of 4.7 and 3.6 kb, corresponding to mRNA originating from transcription initiation sites -1392 and -72, respectively. Screening of a cDNA library derived from phosphate-starved tomato roots yielded three cDNA clones, LCA1A, LCA1B and LCA1C (3.6, 4.5 and 5.1 kb respectively). These cDNAs contain full-length LCA1 mRNA sequence derived from each transcription initiation site, with LCA1C additionally containing an intron of 0.6 kb. Sequence analysis indicated 100% identity between the three size classes of cDNA clones except for the differential 5'-UTR and the unspliced intron. Overall, the results indicate that the two major LCA1 mRNA transcripts are derived by differential transcription initiation and that two of the mRNAs may encode identical protein products, while a third mRNA may correspond to a non-functional truncated protein.
Plant Mol Biol 1999 May
PMID:Alternative transcription initiation sites generate two LCA1 Ca2+-ATPase mRNA transcripts in tomato roots. 1039 52

The antioxidant nordihydroguaiaretic acid (NDGA) inhibited the different sarco/endoplasmic reticulum Ca2+-ATPase isoforms found in skeletal muscle and blood platelets. For the sarcoplasmic reticulum, but not for the blood platelets Ca2+-ATPase, the concentration of NDGA needed for half-maximal inhibition was found to vary depending on the substrate used and its concentration in the assay medium. The phosphorylation of the sarcoplasmic reticulum Ca2+-ATPase by ATP and by Pi were both inhibited by NDGA. In leaky vesicles, measurements of the ATP<-->Pi exchange showed that NDGA increases the affinity for Ca2+ of the E2 conformation of the enzyme, which has low affinity for Ca2+. The effects of NDGA on the Ca2+-ATPase were not reverted by the reducing agent dithiothreitol nor by the lipid-soluble antioxidant butylated hydroxytoluene.
Mol Cell Biochem 1999 May
PMID:Modulation of the low affinity Ca2+-binding sites of skeletal muscle and blood platelets Ca2+-ATPase by nordihydroguaiaretic acid. 1039 87

The slow/cardiac isoform of the sarcoplasmic reticulum Ca2+-ATPase plays an important role in cardiac muscle Ca2+-homeostasis. To determine the native configuration of the SERCA2 ion pump, a chemical cross-linking analysis of heart microsomes was performed. Using one- and two-dimensional immunoblotting following incubation with the hydrophilic probe bis-sulfosuccinimidyl suberate or the hydrophobic crosslinker dithiobis-succinimidyl-propionate, we demonstrate here that SERCA2 forms high-molecular-mass aggregates. In contrast to the Na+/Ca2+-exchanger, Ca2+-ATPase clusters can be stabilized by hydrophilic 1.2 nm crosslinkers and are sensitive to chemical reduction. Hence, the native form of this important Ca2+-regulatory membrane protein involved in cardiac muscle relaxation appears not to exist as a monomeric ion pump unit. Protein-protein interactions might play an important role in the physiological functioning of this Ca2+-ATPase isoform, as has previously been shown for skeletal muscle Ca2+-pumps, Ca2+-binding proteins and Ca2+-channels.
Mol Cell Biol Res Commun 1999 Jun
PMID:Oligomerization of the sarcoplasmic reticulum Ca2+-ATPase SERCA2 in cardiac muscle. 1042 24

The exact chemical composition of the red blood cell (RBC) membrane may vary depending on the methods used to isolate the membrane. We provide evidence here that RBC membrane can be fractionated by differential centrifugation and/or density gradient centrifugation into two distinct types, designated as 'heavy membrane' (HM) and 'light membrane' (LM). The amount of LM is twice that of HM on a per cell basis. HM and LM differ in some biochemical and electrophoretic properties. The total activities of Na+, K+- and Ca2+-ATPases, superoxide dismutase, glutathione peroxidase, catalase and glucose-6-phosphate and 6-phosphogluconate dehydrogenase are significantly higher in LM than HM on a per cell basis. While there is no significant difference in the specific activity of other enzymes between the two membranes, the specific activity of Ca2+-ATPase is significantly higher in HM, whereas Na+,K+-ATPase activity is higher in LM. There is a remarkable difference in the distribution of major ghost polypeptides between these two membranes. Component I of spectrin, component III and a protein with mol. wt. of 165 KDa are present in smaller amounts, whereas component II of spectrin and proteins with mol. wt. of 145, 84 and 76 KDa, respectively, are present in higher amounts in HM than LM. Some proteins such as band 4.1, 48 and 46 KDa are present only in LM, whereas some proteins with mol. wt. of 96, 78 and 43 KDa, respectively are present only in HM. It has been confirmed that these two membranes are not representatives of either (a) right side-out vs. inside out vesicles, or (b) open vs. sealed membranes. Thus HM and LM are two distinct membrane fractions. It is suggested that some part of the membrane is denser than other parts, and during hemolysis of RBCs, the rbc membrane is spliced resulting in two populations, dense and light.
Mol Cell Biochem 1999 Jun
PMID:Heterogeneity of human red blood cell membrane: co-existence of heavy and light membranes. 1044 13

The expression of protein kinase C (PKC) isoforms and the modulation of Ca2+ mobilization by PKC were investigated in the human submandibular duct cell line A253. Three new PKC (nPKC) isoforms (delta, epsilon, and theta) and one atypical PKC (aPKC) isoform (lambda) are expressed in this cell line. No classical PKC (cPKC) isoforms were present. The effects of the PKC activator phorbol 12-myristate-13-acetate (PMA) and of the PKC inhibitors calphostin C (CC) and bisindolymaleimide I (BSM) on inositol 1,4,5-trisphosphate (IP3) and Ca2+ responses to ATP and to thapsigargin (TG) were investigated. Pre-exposure to PMA inhibited IP3 formation, Ca2+ release and Ca2+ influx in response to ATP. Pre-exposure to CC or BSM slightly enhanced IP3 formation but inhibited the Ca2+ release and the Ca2+ influx induced by ATP. In contrast, pre-exposure to PMA did not modify the Ca2+ release induced by TG, but reduced the influx of Ca2+ seen in the presence of this Ca2+-ATPase inhibitor. These results suggest that PKC modulates elements of the IP3/Ca2+ signal transduction pathway in A253 cells by (1) inhibiting phosphatidylinositol turnover and altering the sensitivity of the Ca2+ channels to IP3, (2) altering the activity, the sensitivity to inhibitors, or the distribution of the TG-sensitive Ca2+ ATPase, and (3) modulating Ca2+ entry pathways.
Mol Cell Biochem 1999 Aug
PMID:Modulation of Ca2+ mobilization by protein kinase C in the submandibular duct cell line A253. 1049 76

The inhibition of ion transporting ATPases (Na+,K+-ATPase, Ca2+,Mg2+- and Ca2+-ATPase) by two amphiphilic drugs e.g. chlorpromazine (antipsychotic) and chloroquine (antimalarial) are found to be competitive in nature in vitro with respect to the substrate. Two binding sites - high and low affinity are found to exist on all the three ATPases toward these drugs as evident from the plot of F/F0 vs. different drug concentrations of tryptophan fluorescence of the enzymes. Circular dichroism analysis suggest that binding of drugs to the high affinity site does not involve any change in conformation of ATPase molecules which occur only when drug binds to the low affinity sites. The drug binding sites and possible effect on conformational change of ATPase molecules of these two drugs have been described in this report.
Mol Cell Biochem 1999 Aug
PMID:The effect of binding of chlorpromazine and chloroquine to ion transporting ATPases. 1049 94

The alteration in calcium content and Ca2+-ATPase activity in the brain microsomes of rats with increasing age was investigated. Brain microsomal calcium content was significantly increased in aged rats (50 weeks old) as compared with that of young rats (5 weeks old). Such an increase was not seen in the brain mitochondria of aged rats. Increasing age caused a significant elevation of Ca2+-ATPase activity in the brain microsomes. The microsomal Ca2+-ATPase activity of young rats was significantly decreased by the addition of thapsigargin (10-7-10-5 M), a specific inhibitor of microsomal Ca2+ pump enzyme (Ca2+-ATPase), in the enzyme reaction mixture. The inhibitory effect of thapsigargin (10-5 M) was also seen in the brain microsomes of aged rats. Moreover, the effect of calcium (5 and 10 microM) addition in elevating Ca2+-ATPase activity was not revealed in the microsomes of aged rats, whereas the metal could increase the enzyme activity in young rats, suggesting an involvement of activatory factor on the enzyme with increasing age. The present study demonstrates that ageing induces an increase in thapsigargin-sensitive Ca2+-ATPase activity and a corresponding elevation of calcium content in the brain microsomes. This finding suggests a cellular mechanism by which ageing causes calcium accumulation in brain.
Int J Mol Med 1999 Dec
PMID:Brain microsomal calcium accumulation in rats with increasing age: involvement of thapsigargin-sensitive Ca2+-ATPase. 1056 74

The expression of calcium-binding protein regucalcin and its effect on the microsomal Ca2+-ATPase activity in rat brain tissues was investigated. The expression of regucalcin mRNA was demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) analysis in brain tissues using rat regucalcin-specific primers. Regucalcin concentration in the brain tissues was about 5 x 10(-9)) M as measured using enzyme-linked immunoadsorbent assay (ELISA), and this level was lowered with increasing age (50 weeks old). The presence of regucalcin (10(-9) to 10(-7) M) in the enzyme reaction mixture caused a significant decrease in Ca2+-ATPase activity in the brain microsomes of young rats (5 weeks old). Meanwhile, the enzyme activity was not significantly altered by the addition of calmodulin (1 or 50 microg/ml), calbindin (1 or 10 microg/ml), and S-100 A protein (5 or 25 microg/ml), which are other Ca2+-binding proteins in rat brain. The effect of regucalcin to inhibit microsomal Ca2+-ATPase activity was weakened in the brain of rats with increasing age (50 weeks old). The present study demonstrates that regucalcin is expressed in the brain, and that it can uniquely inhibit Ca2+-ATPase activity in the brain microsomes of rats. The findings suggest that regucalcin plays a role in the regulation of microsomal Ca2+-ATPase activity in rat brain tissues.
Mol Cell Biochem 1999 Oct
PMID:Expression of calcium-binding protein regucalcin and microsomal Ca2+-ATPase regulation in rat brain: attenuation with increasing age. 1056 82

Perinatal hypoxic-ischemic damage remains a major cause of acute mortality in infants. In our study we have shown that ATP-powered calcium pump was degraded in asphyxiated erythrocyte membranes. Moreover, the activity of Ca2+-ATPase, the enzyme that is solely responsible for maintenance of calcium homeostasis in erythrocytes, was reduced by 50% compared to healthy newborns. We have also detected the enhanced lipid peroxidation in asphyxiated erythrocyte ghosts. To elucidate the potential mechanisms of the calcium pump damage, we have examined the effect of peroxynitrite on Ca2+-ATPase purified from adult human erythrocyte membranes. We have concluded that calcium pump is a direct target for peroxynitrite action in vitro. Our results indicate that erythrocyte membrane compounds could be a primary target for asphyxia-induced damage, and the impairment of the plasma membrane Ca2+-ATPase function could be, in part, mediated by reactive oxygen species.
Mol Cell Biol Res Commun
PMID:Characterization of erythrocyte compounds in asphyxiated newborns. 1066 95


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