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)

The amino acid sequences of 15 sugar permeases of the bacterial phosphoenolpyruvate-dependent phosphotransferase system (PTS) were divided into four homologous segments, and these segments were analyzed to give phylogenetic trees. The permease segments fell into four clusters: the lactose-cellobiose cluster, the fructose-mannitol cluster, the glucose-N-acetylglucosamine cluster, and the sucrose-beta-glucoside cluster. Sequences of the glucitol and mannose permeases (clusters 5 and 6, respectively) were too dissimilar to establish homology with the other permeases, but short regions of statistically significant sequence similarities were noted. The functional and structural relationships of these permease segments are discussed. Some of the homologous PTS permeases were found to exhibit sufficient sequence similarity to subunits 4 and 5 of the eukaryotic mitochondrial NADH dehydrogenase complex to suggest homology. Moreover, subunits 4 and 5 of this complex appeared to be homologous to each other, suggesting that these PTS and mitochondrial proteins comprise a superfamily. The integral membrane subunits of the evolutionarily divergent mannose PTS permease, the P and M subunits, exhibited limited sequence similarity to subunit 6 of the mitochondrial F1F0-ATPase and subunit 5b of cytochrome oxidase, respectively. These results suggest that PTS sugar permeases and mitochondrial proton-translocating proteins may be related, although the possibility of convergent evolution cannot be ruled out.
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PMID:Evolutionary relationships among the permease proteins of the bacterial phosphoenolpyruvate: sugar phosphotransferase system. Construction of phylogenetic trees and possible relatedness to proteins of eukaryotic mitochondria. 192 Apr 54

To establish the difference of mechanism between irritative and paralytic nystagmus, alterations of Na-K-ATPase and succinic dehydrogenase activity in the vestibular sensorineural elements were investigated for 20 guinea pigs, and glucose uptake of the vestibular nuclei for 13 guinea pigs were measured by the [14C]-2-deoxy-D-glucose method. Irritative and paralytic nystagmus were experimentally provoked by introducing K+ into the perilymphatic space. From the results it was concluded that irritative nystagmus is provoked by increased excitability of vestibular sensory cells, while paralytic nystagmus is provoked by decreased excitability. However, the direction of nystagmus was eventually decided by the tonus imbalance between the bilateral vestibular nuclei. The ipsilateral vestibular nucleus was predominant during irritative nystagmus, while the contralateral vestibular nucleus was predominant during paralytic nystagmus.
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PMID:The mechanism of irritative nystagmus and paralytic nystagmus. A histochemical study of the guinea pig's vestibular organ and an autoradiographic study of the vestibular nuclei. 192 91

Glucose transport in the bloodstream form of the protozoan parasite Trypanosoma brucei was characterized by enzymatically measuring the D-glucose uptake. Uptake kinetics showed a concentration-dependent saturable process, typical for a carrier-mediated transport system, with an apparent Km = 0.49 +/- 0.14 mM and Vmax = 252 +/- 43 nmol.min-1.mg cell protein-1 (equal to 2.25 x 10(8) trypanosomes). The specificity of glucose transport was investigated by inhibitor studies. Glucose uptake was shown to be sodium independent; neither the Na+/K(+)-ATPase inhibitor ouabain (1 mM) nor the ionophor monensin (1 microM) inhibited uptake. Transport was also unaffected by the H(+)-ATPase inhibitor N,N'-dicyclohexylcarbodiimide (DCCD; 20 microM) and the uncoupler carbonylcyanide-4-(trifluoromethoxy)phenylhydrazone (FCCP; 1 microM). However, highly significant inhibition was obtained with both phloretin (82% at 0.13 mM; Ki = 64 microM) and cytochalasin B (77% at 0.3 mM; Ki = 0.44 mM), and partial inhibition with phlorizin (14% at 0.5 mM; Ki = 3.0 mM). In each case, inhibition was noncompetitive, partially reversible (45%) for phloretin and completely reversible for cytochalasin B and phlorizin. Measurement of the temperature-dependent glucose uptake between 25 degrees C and 37 degrees C resulted in a temperature quotient of Q10 = 1.97 +/- 0.02 and an activation energy of Ea = 52.12 +/- 1.00 kJ/mol for glucose uptake. We conclude that glucose uptake in T. brucei bloodstream forms occurs via a facilitated diffusion system, clearly distinguished from the human erythrocyte-type glucose transporter with about a 10-fold higher affinity for glucose and about a 1000-fold decreased sensitivity to the inhibitor cytochalasin B.
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PMID:Specificity of glucose transport in Trypanosoma brucei. Effective inhibition by phloretin and cytochalasin B. 193 76

The transport of glucose by canine thick ascending limbs (TAL) and inner medullary collecting ducts (IMCD) was studied using tubule suspensions and membrane vesicles. The uptake of D-[14C(U)]glucose by a suspension of intact TAL tubules was reduced largely by phloretin (Pt), moderately by phlorizin (Pz), and completely suppressed by a combination of both agents. A selective effect of Pz on the transport of [14C]alpha-methyl-D-glucoside, but not on 2-[3H]deoxyglucose, was also observed in TAL tubules. In contrast, glucose transport was unaffected by Pz but entirely suppressed by Pt alone in IMCD tubules. The metabolism of glucose was largely suppressed by Pt but unaffected by Pz in both types of tubules. Membrane vesicles were prepared from the red medulla and the white papilla or from TAL and IMCD tubules isolated from these tissues. Vesicle preparations from both tissues demonstrated a predominant carrier-mediated, sodium-independent, Pt- and cytochalasin B-sensitive glucose transport. Following purification of basolateral membrane on a Percoll gradient, the sodium-insensitive D-[14C(U)]glucose transport activity copurified with the activity of the basolateral marker Na(+)-K+ ATPase in both tissues. However, a small sodium-dependent and Pz-sensitive component of glucose transport was found in membrane vesicles prepared from the red medulla or from thick ascending limb tubules but not from the papilla nor collecting duct tubules. The kinetic analysis of the major sodium-independent processes showed that the affinity of the transporter for glucose was greater in collecting ducts (Km = 2.3 mM) than in thick ascending limbs (Km = 4.9 mM). We conclude that glucose gains access into the cells largely through a basolateral facilitated diffusion process in both segments. However a small sodium-glucose cotransport is also detected in membranes of TAL tubules. The transport of glucose presents an axial differentiation in the affinity of glucose transporters in the renal medulla, ensuring an adequate supply of glucose to the glycolytic inner medullary structures.
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PMID:Basolateral glucose transport in distal segments of the dog nephron. 195 66

The effects of inhibition of bone resorption by the peptide hormone calcitonin have been studied at the level of the osteoclast. Although not epithelial, the osteoclast is polarized with the secretion of newly synthesized lysosomal enzymes and of acid occurring specifically at the apical pole, facing the bone compartment. The membranes composing the apical (ruffled-border) and basolateral domains contain topologically restricted antigens, a 100 x 10(3) Mr lysosomal membrane protein and the Na+,K(+)-ATPase, respectively. It was found that calcitonin induces a rapid (15-60 min) redistribution of the apical marker as well as of markers of the secretory compartment of the osteoclast (arylsulfatase and cation-independent mannose 6-phosphate (Man6P) receptors). The apical plasma membrane, in contrast to the basolateral membrane, is selectively internalized. This internalization leads to the disappearance of the ruffled border. The vesicular translocation of apical membranes is reminiscent of the events occurring in gastric oxyntic cells and in kidney tubule intercalated cells during the regulation of acid secretion. In parallel, the synthesis of both the lysosomal enzyme arylsulfatase and Man6P receptors is arrested. The products that were already present in the secretory pathway seem to be rerouted to intracellular vacuoles instead of being targeted to the plasma membrane, leading to marked accumulation of enzymes in the inhibited cells. These results suggest that the rapid inhibition of bone resorption by calcitonin involves the vesicular translocation of the apical membranes and the rapid arrest in the synthesis and secretion of lysosomal enzymes in osteoclasts.
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PMID:Selective internalization of the apical plasma membrane and rapid redistribution of lysosomal enzymes and mannose 6-phosphate receptors during osteoclast inactivation by calcitonin. 196 25

Sodium artesunate (SA), a synthetic derivative of artemisinin first isolated in China, is a water soluble antimalaria used clinically in China. The jejunum of mouse was mounted in Ussing chambers and bathed in NaCl Ringer. There was a potential difference (PD) across the intestinal wall with the serosa being positive. Addition of SA to the mucosal side of the D-glucose (5.5 mmol/L) NaCl Ringer bathing solution, caused a significant decrease in both PD and short circuit current (I(sc)). However, SA had little effect when added to the glucose free Ringer bathing solution. SA 0.1-1.0 mmol/L caused a decrease in Na+,K(+)-ATPase activities in vitro. The results suggest that the inhibitory effect on the electrical properties of mouse jejunum is associated with the inhibition of Na+,K(+)-ATPase activities.
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PMID:[Effects of sodium artesunate on electrical properties and Na+,K(+)-ATPase activities of mouse small intestine]. 196 74

In order to refine further our structural model of the coated vesicle (H+)-ATPase (Arai, H., Terres, G., Pink, S., and Forgac, M. (1988) J. Biol. Chem. 263, 8796-8802), we have extended our structural analysis to identify peripheral and glycosylated subunits of the pump as well as to identify subunits which are in close proximity in the native (H+)-ATPase complex. Treatment of the purified, reconstituted (H+)-ATPase with 0.30 M KI in the presence or absence of ATP or MgATP results in the release of the 73-, 58-, 40-, 34-, and 33-kDa subunits, leaving behind the 100-, 38-, 19-, and 17-kDa subunits in the membrane. Because the former group of polypeptides is released from the membrane in the absence of detergent, they correspond to peripheral membrane proteins. To determine which subunits are in close proximity, cross-linking of the purified (H+)-ATPase was carried out using the cleavable, bifunctional amino reagent 3,3'-dithiobis(sulfosuccinimidylpropionate) followed by two-dimensional gel electrophoresis. These studies indicate that contact regions exist between the 73- and 58-kDa subunits as well as between the 17-kDa subunit and the 40-, 34-, and 33-kDa subunits. To test for glycosylation of the (H+)-ATPase, the detergent-solubilized complex was treated with neuraminidase followed by electrophoresis and blotting using a peanut lectin/horseradish peroxidase conjugate. Galactose-inhibitable staining of the 100-kDa subunit, together with affinity chromatography of the intact (H+)-ATPase on peanut lectin agarose, indicates that the 100-kDa subunit is glycosylated, most likely at a site exposed on the luminal side of the membrane. These results, together with those presented in the preceding paper (Adachi, I., Arai, H., Pimental, R., and Forgac, M. (1990) J. Biol. Chem. 265, 960-966), were used in the construction of a refined model of the coated vesicle (H+)-ATPase.
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PMID:Dissociation, cross-linking, and glycosylation of the coated vesicle proton pump. 196 52

Enprostil is a prostaglandin E2 analogue characterized as a racemic mixture of four stereoisomers. Enprostil and a single isomer, RS-86505-007, were evaluated for their effects on the permeability of actively and passively transported compounds in segments of small intestine from rabbits and monkeys. Consistent with human in-vivo studies, which have demonstrated decreases in absorption of D-xylose, both compounds inhibited D-glucose transport. The passively transported compounds mannitol and progesterone were also less permeable in this model in the presence of enprostil or RS-86505-007. In contrast to the concentration-dependent inhibition displayed by ouabain, RS-86505-007 had no effect on purified Na+K(+)-ATPase. It is suggested that an effect of a general nature, possibly an increase in the barrier properties at the intestinal surface, may explain the transport inhibition. Of two other enprostil isomers, RS-86812-007 inhibited D-glucose transport in rabbit small intestine, while RS-86505-008 had no effect. The prostaglandin E1 analogue misoprostol was ineffective in monkey and poorly effective in rabbit. This suggests that the inhibition of D-glucose transport by enprostil and its active stereoisomers is mediated through some structurally specific receptor interaction.
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PMID:The effects of enprostil and RS-86505-007 on in-vitro intestinal permeability of rabbit and monkey. 196 48

The effect of chronic hyperglycemia and polyol pathway activation on the Schwann cell has not been resolved although injury to this cell has long been suspected in diabetic neuropathy. Hyperglycemia, resulting from galactose intoxication of four months duration, induces dose-dependent accumulations of endoneurial fluid sodium and chloride that are linked to polyol pathway activity and associated with dose-dependent increases in sciatic nerve water content, endoneurial fluid pressure and (Na+, K+)-ATPase activity. In order to understand the impact of these changes on the nerve microenvironment, cellular elements of the endoneurium were quantitatively and qualitatively assessed in rats receiving 0%, 10%, 20% or 40% galactose diets. After four months of galactose intoxication, dose-dependent changes in the size distribution of myelinated nerve fibers were apparent. A shift in size-frequency histograms of galactose-intoxicated animals towards smaller fibers was accompanied by a decrease in axon diameter and the volume fraction ratio of axon to myelinated nerve fibers. In the sciatic nerve of all 40% galactose-fed rats examined by electron microscopy, Schwann cells of myelinated fibers showed both reactive and degenerative changes. Demyelination was preceded by splitting at the intraperiod line. Remyelination was identified by axons with disproportionately thin myelin sheaths. Axonal dystrophy and degeneration were infrequently seen, but there was axonal regeneration. Dose-dependent increases in mast cell number were observed with degranulation apparent in rats receiving 20% and 40% galactose. Endothelial cell number and basal lamina thickness were increased in the endoneurial vessels of galactose-intoxicated rats. Increased cytoplasmic area and degenerative changes in pericytes were also noted. These observations indicate that significant morphologic changes accompany the hyperosmotic imbalance resulting from galactose intoxication of four months duration. Schwann cell injury and demyelination are present in a disorder linked to polyol metabolism since aldose reductase, the anabolic enzyme of the polyol pathway, is localized to this myelin-forming cell.
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PMID:Cellular pathology of the nerve microenvironment in galactose intoxication. 202 66

This study concerns the assembly into a multisubunit enzyme complex of a small hydrophobic protein imported into isolated mitochondria. Subunit 8 of yeast mitochondrial ATPase (normally a mitochondrial gene product) was expressed in vitro as a chimaeric precursor N9L/Y8-1, which includes an N-terminal-cleavable transit peptide to direct its import into mitochondria. Assembly into the enzyme complex of the imported subunit 8 was monitored by immunoadsorption using an immobilized anti-F1-beta monoclonal antibody. Preliminary experiments showed that N9L/Y8-1 imported into normal rho+ mitochondria, with its complement of fully assembled ATPase, did not lead to an appreciable assembly of the exogenous subunit 8. With the expectation that mitochondria previously depleted of subunit 8 could allow such assembly in vitro, target mitochondria were prepared from genetically modified yeast cells in which synthesis of subunit 8 was specifically blocked. Initially, mitochondria were prepared from strain M31, a mit- mutant completely incapable of intramitochondrial biosynthesis of subunit 8. These mit- mitochondria however were unsuitable for assembly studies because they could not import protein in vitro. A controlled depletion strategy was then evolved. An artificial nuclear gene encoding N9L/Y8-1 was brought under the control of a inducible promoter GAL1. This regulated gene construct, in a low copy number yeast expression vector, was introduced into strain M31 to generate strain YGL-1. Galactose control of the expression of N9L/Y8-1 was demonstrated by the ability of strain YGL-1 to grow vigorously on galactose as a carbon source, and by the inability to utilize ethanol alone for prolonged periods of growth. The measurement of bioenergetic parameters in mitochondria from YGL-1 cells experimentally depleted of subunit 8, by transferring growing cells from galactose to ethanol, was consistent with the presence in mitochondria of a mosaic of ATPase, namely fully assembled functional ATPase complexes and partially assembled complexes with defective F0 sectors. These mitochondria demonstrated very efficient import of N9L/Y8-1 and readily incorporated the imported processed subunit 8 protein into ATPase. Comparison of the kinetics of import and assembly of subunit 8 showed that assembly was noticeably delayed with respect to import. These findings open the way to a new systematic analysis of the assembly of imported proteins into multisubunit mitochondrial enzyme complexes.
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PMID:Assembly of imported subunit 8 into the ATP synthase complex of isolated yeast mitochondria. 213 40


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