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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The (Ca(2+)-Mg2+)ATPase activity in microsomes of Schistosoma mansoni is fully inhibited by vanadate (I50 = 2.5 microM). 45Ca2+ is accumulated within microsomal vesicles in an ATP-dependent process that is enhanced 5-fold in the presence of 40 mM phosphate. Accumulated 45Ca2+ is rapidly released by 5 microM of the Ca2+ ionophore A23187 (t1/2 less than or equal to 6 s). (Ca(2+)-Mg2+)ATPase activity and Ca2+ uptake share the same subcellular distribution pattern and similar Ca2+ sensitivities (K0.5 = 0.39 microM and 0.15 microM, respectively). The substrate selectivity is high for both ATPase activity and Ca2+ transport. These results indicate the presence of an active transport of Ca2+ coupled to the (Ca(2+)-Mg2+)ATPase activity previously described in this parasite. A plasma membrane localization and physiological role in calcium homeostasis are suggested.
Mol Biochem Parasitol 1992 Jun
PMID:A (Ca(2+)-Mg2+)ATPase from Schistosoma mansoni is coupled to an active transport of calcium. 153 90

When isolated from chick oviduct cytosol by antibody adsorption, the inactive progesterone receptor is associated with the two heat shock proteins, hsp90 and hsp70, plus three additional proteins termed p54, p50, and p23 according to their molecular weights. While their functions remain unknown, all of these receptor associated proteins are dissociated upon receptor activation in intact cells. To better understand the assembly and activation mechanisms of progesterone receptor complexes, we have developed a cell-free system for studying receptor interactions with hsp90 and hsp70 and have used this system to examine requirements for hsp90 binding to the receptor. Purified receptor, free of hsp90 and immobilized on an antibody affinity resin, will rebind hsp90 in rabbit reticulocyte lysate when several conditions are met. These include: (1) absence of progesterone, (2) elevated temperature (30 degrees C), (3) presence of ATP, and (4) presence of Mg2+. We have obtained maximal hsp90 binding to receptor when lysate is supplemented with 3 mM MgCl2 and an ATP regenerating system. ATP depletion of lysate by dialysis or ATPase addition blocks hsp90 binding to the receptor. When progesterone is added to pre-formed receptor complexes in reticulocyte lysate it promotes activation and the dissociation of hsp90. This process is also dependent upon ATP. Thus, both the assembly, and activation of the progesterone receptor can be accomplished in the reticulocyte lysate system.
J Steroid Biochem Mol Biol 1992 Mar
PMID:Composition, assembly and activation of the avian progesterone receptor. 156 3

Highly co-operative structural transitions and conformational changes can be directly observed in bundles of filaments formed by the RecA protein of Escherichia coli. These filaments have been formed with RecA protein, DNA and the ATP analog adenosine 5'-O-(3-thiotriphosphate) (ATP-gamma-S). We show that while ATP-gamma-S has frequently been called non-hydrolyzable in the RecA literature, it is hydrolyzed by RecA with a kcat of about 0.01 to 0.005 min-1. This rate of ATP-gamma-S hydrolysis is significant to structural studies conducted on a time scale of hours. It has been shown that RecA subunits may be seen in different conformations within one particular form of RecA bundle. We now show that additional structural transitions take place within these bundles when they are allowed to incubate at 37 degrees C for several hours. This is the same time scale on which ATP-gamma-S is being hydrolyzed, and the suggestion that the observed structural transitions arise from the hydrolysis of ATP-gamma-S is supported by the fact that when the hydrolysis of ATP-gamma-S is inhibited (at 4 degrees C), the transitions are not observed. The transitions that occur are highly co-operative, with filaments as a whole changing their state over lengths of several thousand Angstroms. This shows that RecA filaments have an internal co-operativity, and we suggest that this is important to their function in vivo. The motions of subunits that we visualize appear to be mainly rotational, and this can be used to infer information about the motions of RecA subunits associated with the RecA ATPase that occurs during the DNA strand exchange reaction.
J Mol Biol 1992 May 05
PMID:Direct visualization of dynamics and co-operative conformational changes within RecA filaments that appear to be associated with the hydrolysis of adenosine 5'-O-(3-thiotriphosphate). 158 90

The formation of palmitoylcarnitine is catalyzed by carnitine palmitoyl-transferase (CPT-I) and this catalysis is the first committed step in beta-oxidation. The malonyl-CoA-inhibited isoform appears to be distinct from latent (CPT-II) activity, which is localized to the matrix side of the mitochondrial inner membrane. Sarcoplasmic reticulum from canine cardiac muscle was fractionated on a discontinuous sucrose density gradient into three major bands, all of which contained Ca(2+)-ATPase activity. Only the fraction that banded at a concentration of 38% surcrose was slightly contaminated by mitochondria. Peroxisomal uricase was low or absent in fractionated SR. All sarcoplasmic reticulum fractions contained malonyl-CoA-sensitive medium- (COT) and long-chain (CPT) carnitine acyltransferase activities. CPT activity decreased in sarcoplasmic reticulum when Triton X-100 was present. Carnitine acyltransferase activities were inactivated by preincubating the sarcoplasmic reticulum with the sulfhydryl reagent, 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB). In contrast, mitochondrial CPT-II activity was stable in the presence of DTNB and activated by Triton X-100. Western blots of mitochondria and sarcoplasmic reticulum fractions showed that the mitochondrial fractions reacted with antibody to mitochondrial CPT-II but not with SR protein when both were added at comparable specific activities. The data suggest that cardiac SR contains a unique malonyl-CoA-sensitive isoform of CPT, and that synthesis of acylcarnitine may occur in the microenvironment of Ca2+ transport, where the extent of production of acylcarnitine is controlled by cardiac acetyl-CoA carboxylase activity.
J Mol Cell Cardiol 1992 Mar
PMID:Evidence for malonyl-CoA-sensitive carnitine acyl-CoA transferase activity in sarcoplasmic reticulum of canine heart. 162 48

Intermediate and short stumpy bloodstream forms of Trypanosoma brucei brucei are transitional stages in the differentiation of mammal-infective long slender bloodstream forms into the procyclic forms found in the midgut of the tsetse vector. Although the mitochondria of the proliferative long slender forms do not accumulate rhodamine 123, the mitochondria of the transitional forms attain this ability thus revealing the development of an electromotive force (EMF) across the inner mitochondrial membrane. The EMF is inhibited by 2,4-dinitrophenol, rotenone and salicylhydroxamic acid but not by antimycin A or cyanide. Consequently, NADH dehydrogenase, site I of oxidative phosphorylation, is the source of the EMF and the plant-like trypanosome alternative oxidase (TAO) supports the electron flow serving as the terminal oxidase of the chain. Although the TAO is present in the long slender forms as well, it serves only as the terminal oxidase for electrons from glycerol-3-phosphate dehydrogenase. The data presented here, combined with older data, lead to the conclusion that the mitochondria of transitional intermediate and short stumpy forms likely produce ATP. This putative production is either by F1F0 ATPase driven by the complex I proton pump or by mitochondrial substrate level phosphorylation, or most likely by both. These conclusions contrast with the previously held dogma that all bloodstream form mitochondria are incapable of ATP production.
Mol Biochem Parasitol 1991 Apr
PMID:Mitochondrial development in Trypanosoma brucei brucei transitional bloodstream forms. 164 58

Isolated rat hepatocytes possess a saturable glucocorticoid uptake system with high affinity (Kd value = 2.8 +/- 0.7 x 10(-8) M; 318,000 +/- 80,000 binding sites per cell; 317 fmol/mg protein). The initial rates of uptake decrease by about 30-40% if the cells are incubated simultaneously with [3H]corticosterone and either SH-reagents (N-ethylmaleimide and p-chloromercuriphenylsulphonate, 1 mM), metabolic inhibitors (2,4-dinitrophenol, 1 mM; and antimycin, 0.1 mM) or the Na+/K(+)-ATPase-inhibitors, ouabain and quercetine. These Na+/K(+)-ATPase-blockers exert half-maximal inhibition at 3 x 10(-7) and 3 x 10(-6) M, respectively. A slight increase in K+ concentration and a corresponding decrease in Na+ in the medium leads to a significant reduction in the initial uptake rate. The uptake system from the rat hepatocytes shows a clear steroid specificity, being different from the intracellular receptor. Corticosterone and progesterone are the strongest competitors, cortisol, 5 alpha- and 5 beta-dihydrocorticosterone, 11-deoxycorticosterone, cortisone and testosterone have an intermediate effect and only weak competition is exerted by dexamethasone and by the mineralocorticoid, aldosterone. Estradiol and estrone sulphate as well as the synthetic glucocorticoid triamcinolone acetonide are unable to inhibit initial corticosterone uptake.
J Steroid Biochem Mol Biol 1991 Jun
PMID:Uptake of corticosterone into isolated rat liver cells: possible involvement of Na+/K(+)-ATPase. 164 77

1. We have used in situ hybridization techniques to determine the mRNA for (Na + K)ATPase in 20 brain regions from control rats and rats treated with high doses of deoxycorticosterone (DOC). 2. DOC-treated rats developed a salt appetite following the second hormone administration on alternate days and were used after the fourth DOC administration. 3. DOC treatment did not change the number of silver grains/cell deposited in cells from Ca1, CA2, CA3, and CA4 hippocampal subfields, dentate gyrus, cerebral cortex, medial preoptic area (POA), substantia nigra, and periventricular gray matter. 4. Nonsignificant reductions were detected in lateral POA, medial and lateral septum, caudate-putamen, and three amygdaloid nuclei (cortical, basolateral, and central) from DOC-treated rats. 5. Significant reductions were obtained, after DOC administration, in arcuate and ventromedial hypothalamic nuclei and medial and lateral amygdala. 6. The results suggested that regulation of the beta-subunit mRNA of (Na + K)-ATPase may be related to the central actions of mineralocorticoids in the control of salt intake.
Cell Mol Neurobiol 1991 Jun
PMID:Effects of deoxycorticosterone treatment on beta-subunit mRNA for (Na + K)ATPase in brain regions determined by in situ hybridization. 165 Nov 64

The induction of polycystic kidney disease (PKD) by glucocorticoids in newborn mice behaves as a "threshold" trait, with prevalence of PKD varying in different inbred strains after exposure to an inducing steroid. C3H mice (low threshold for PKD) demonstrated greater specific dexamethasone binding than DBA mice (high threshold) on the second day of life. Treatment with methylprednisolone acetate (MPA), a cyst-inducing steroid, down regulated dexamethasone binding earlier than in DBA mice. C3H mice demonstrated greater whole kidney homogenate Na-K ATPase activity than DBA mice within 24h of MPA injection. Specific renal glucocorticoid binding may be a regulator of threshold for murine glucocorticoid induced PKD. Our findings support in vitro evidence that glucocorticoid induced Na-K ATPase activity during critical periods of nephron development is an important regulatory point of this model.
J Steroid Biochem Mol Biol 1991 Aug
PMID:Ontogeny of dexamethasone binding and sodium potassium ATPase activity in experimental murine polycystic kidney disease. 165 92

The (Ca2+ + Mg2+) ATPase which serves as a Ca2+ pump in the kidney basolateral membranes is essential to the maintenance of an intracellular Ca2+ concentration optimal for kidney function. Since atrial natriuretic peptide (ANP) is known to participate in the Ca2+ homeostasis mechanism, altered levels of ANP in diabetes may vary the pump activity and consequently the kidney function. In order to examine the modulatory role of ANP on (Ca2+ + Mg2+) ATPase in short- (6 weeks) and long-term (6 months) diabetes, rats were injected with streptozotocin (65 mg/kg body wt, i.v.). At 6 weeks, the plasma ANP was decreased whereas, ANP-receptor binding in the kidney basolateral membrane was increased. In contrast, there was an increased plasma ANP and decreased ANP receptor binding at 6 months. Insulin treatment to diabetic animals normalized these parameters. The (Ca2+ + Mg2+) ATPase activity was unchanged both at 6 weeks and 6 months. Our results demonstrate that the unchanged Ca2+ pump activity in short-term and long-term diabetes serves to maintain the Ca2+ homeostasis in the kidney cells and thus may maintain the hyperfiltration state in diabetes. Unaltered (Ca2+ + Mg2+) ATPase is achieved by the initial up-regulation and subsequent down-regulation of the ANP receptors.
Mol Cell Biochem 1991 Jun 26
PMID:(Ca2+ + Mg2+) ATPase activity in kidney basolateral membrane in diabetes: role of atrial natriuretic peptide. 165

The purpose of this study was to determine if selected biochemical parameters representing the contractile and calcium regulating systems of cardiac muscle scaled among mammals having inherently different resting heart rates (RHR). Eight mammalian species with RHR ranging from 51 to 475 beats per minute (bpm) were studied. The oxidative capacity of the myocardium is highly correlated with the RHR. The hypothesis of the present study was that the capacities of the energy utilizing processes of contraction and calcium regulation would also be correlated to the functional demand imposed on the muscle as represented by the RHR. Myosin (M) and myofibrillar (MF) ATPase activities, myosin isoenzyme distribution and sarcoplasmic reticulum (SR) ATPase activity were determined. Animals with RHR above 300 bpm express V1 myosin while animals with lower RHR express primarily V3. M and MF ATPase activities correlated with RHR, but the major difference in activities occurred at the 'threshold' RHR of about 300 bpm at which the switch from V3 to V1 appears to occur. SR ATPase activity per mg of microsomal protein was for the most part constant among different mammals, but the SR ATPase activity per g of heart tissue was significantly correlated with RHR as slower beating hearts tended to yield less SR protein per unit mass. We conclude that both the contractile and calcium regulating systems are scaled to the functional parameter of RHR among different mammals. The contractile system uses a slow myosin ATPase isoform at low resting heart rates whereas above the postulated threshold RHR of about 300 bpm a switch in gene expression to a fast myosin ATPase isoform occurs.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem 1991 Aug 14
PMID:Contractile and calcium regulating capacities of myocardia of different sized mammals scale with resting heart rate. 165 10


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