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)

High-affinity Ca(2+)-activated ATPases that do not show any demonstrable dependence on Mg2+ have been reported in the plasma membranes of different trypanosomatids, and it has been suggested [McLaughlin (1985) Mol. Biochem. Parasitol. 15, 189-201; Ghosh, Ray, Sarkar & Bhaduri (1990) J. Biol. Chem. 265, 11345-11351] that these enzymes may have a role in Ca2+ transport by the plasma membrane and in the regulation of intracellular Ca2+ in these parasites. In this report we investigated Ca2+ transport by Trypanosoma cruzi plasma membrane vesicles using Arsenazo III as a Ca2+ indicator. These vesicles accumulated Ca2+ upon addition of ATP only when Mg2+ was present and released it in response to the Ca2+ ionophore A23187, but were insensitive to inositol 1,4,5-trisphosphate. Ca2+ transport was insensitive to antimycin A, oligomycin and carbonyl cyanide p-trifluorophenylhydrazone, ruling out any mitochondrial contamination. Staurosporine and phorbol myristate acetate had no effect on this activity, while low concentrations of vanadate (10 microM) completely inhibited it. In addition, we describe a high-affinity vanadate-sensitive (Ca(2+)-Mg2+)-ATPase in the highly enriched plasma membrane fraction of T. cruzi. Kinetic studies indicated that the apparent Km for free Ca2+ was 0.3 microM. On the other hand, Ca(2+)-ATPase activity and Ca2+ transport were both stimulated by bovine brain calmodulin and by endogenous calmodulin purified from these cells. In addition, trifluoperazine and calmidazolium, at concentrations in the range in which they normally exert anti-calmodulin effects, inhibited the calmodulin-stimulated Ca(2+)-ATPase activity. These observations support the notion that a Mg(2+)-dependent plasma membrane Ca2+ pump is present in these parasites.
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PMID:A calmodulin-activated (Ca(2+)-Mg2+)-ATPase is involved in Ca2+ transport by plasma membrane vesicles from Trypanosoma cruzi. 183 15

Cytochrome c-oxidase type aa3 (EC 1.9.3.1) was purified to homogeneity from vegetative Bacillus cereus by ion-exchange and hydroxylapatite chromatography in the presence of Triton X-100. Gel filtration analysis suggested a dimeric structure apparently 172 kDa in size; however, only a monomer of 81 kDa was detected when analysed by non-denaturing gel electrophoresis. Denaturing gel electrophoresis analysis of the protein showed the presence of two subunits (51 and 30 kDa). Atomic absorption and visible spectroscopy showed typical aa3 redox centres with haem a iron and copper in a ratio of 22 nmol and 35 ng-atom per mg protein, respectively. No haem c was found associated with the purified enzyme in the conditions reported here. Oxidase activity was fully reconstituted by phospholipids in the presence of N,N,N',N'-tetramethyl-p-phenylenediamine or reduced yeast cytochrome c (but not horse cytochrome c) as electron donors. This activity was abolished by cyanide and carbon monoxide.
Mol Microbiol 1991 Jan
PMID:Purification and characterization of two-subunit cytochrome aa3 from Bacillus cereus. 184 7

Acute myocardial ischemia provokes sensitization of the adenylyl cyclase system. This sensitization can be differentiated in a receptor-specific and an enzyme-specific sensitization. The receptor-linked sensitization is characterized by an increase of beta-adrenergic receptors in the plasma membranes after 15 mins of global ischemia (49.8 +/- 3.6 to 67 +/- 6 fmol/mg protein) followed by a further increase (89 +/- 4 fmol/mg protein) after 50 min of ischemia in isolated perfused hearts. Concomitantly functionally coupled receptors which are able to bind the beta-agonist with high affinity, increased by 32% after 15 min and by 57% after 50 min of ischemia. The affinities of the receptors for their agonists or their antagonists remain unchanged. Maximally isoproterenol-stimulated adenylyl cyclase activity rose from 66 +/- 7 to 101 +/- 10 pmol cAMP/min/mg protein after 15 min of global ischemia indicating the beta-receptor-specific sensitization of the beta-adrenergic system. This sensitization was followed by a gradual decline of the adenylyl cyclase activity after 30 and 50 min of global ischemia. Additionally, 15 min of myocardial ischemia induced an enzyme-linked sensitization of the adenylyl cyclase activity as indicated by an increase of the forskolin-stimulated activity by about 25% (300 +/- 20 vs 378 +/- 25 pmol cAMP/min/mg protein). In contrast after 50 min of ischemia the total adenylyl cyclase activity declined (232 +/- 24 pmol cAMP/min/mg protein) despite the persistent increase of beta-adrenergic receptors in the plasma membranes. These data demonstrate that the enzyme-specific sensitization is only transient. The early sensitization and late inactivation of the adenylyl cyclase activity occurred independently of receptor activation and could not be prevented by beta-blockade (10(-6) M alprenolol). Cyanide perfusion (1 mM), used to block energy metabolism, lead to energy depletion similar to acute myocardial ischemia. This resulted in an increase of functionally coupled receptors with a time course comparable to that of global ischemia. Additional perfusion with desensitizing concentrations of the beta-agonist isoproterenol did not induce uncoupling or internalization of beta-adrenergic receptors in cyanide treated hearts, suggesting that the rise in functionally coupled receptors is due to a redistribution in part caused by the abolition of continuous receptor internalization. In contrast, the enzyme-linked sensitization is independent of cellular localization of the beta-adrenergic receptors. The increased activity was carried by the enzyme even after partial purification with solubilization and wheat germ affinity chromatography. These data suggest an ischemia-induced, covalent modification of the adenylyl cyclase.(ABSTRACT TRUNCATED AT 400 WORDS)
J Mol Cell Cardiol 1990 Dec
PMID:Dual sensitization of the adrenergic system in early myocardial ischemia: independent regulation of the beta-adrenergic receptors and the adenylyl cyclase. 196 11

Calcium is believed to provide feedback between myocardial energy consumption and production. Calcium content was proved to increase in mitochondria (MT) isolated from (1) stimulated hearts, and (2) hearts of increased contractility. In this work we compared Ca2+ content in the intact MT of skinned strips excised at 0 degrees C from previously stimulated or rested guinea-pig ventricles equilibrated with 45Ca and in single rested or stimulated myocytes. In both preparations Ca2+ was released from MT by means of CCCP (carbonyl cyanide m-chlorophenyl-hydrazone; 100 microM). CCCP released 1.58 +/- 0.55 nmol Ca2+/mg of MT protein from the strips of rested hearts and 3.86 +/- 1.12 nmol Ca2+/mg of MT protein from the stimulated muscles. Stimulated myocytes responded to the close micro-injection of CCCP with transient contracture which was not inhibited by caffeine (10 mM) or ryanodine (0.1 microM, 45 min), although the time-course of the contracture was changed. Contracture could not be initiated in rested cells. It is suggested that in rested myocytes MT contain much less Ca2+ than in stimulated ones.
J Mol Cell Cardiol 1991 Feb
PMID:Calcium in the in situ mitochondria of rested and stimulated myocardium. 206 28

In order to trace possible accumulations of mercury, three vervet monkeys received occlusal amalgam fillings, three others maxillary bone implants of amalgam, and three untreated monkeys served as controls. One year later all animals were sacrificed by transcardial perfusion with glutaraldehyde. Tissue sections from different organs were subjected to silver amplification by autometallography and analyzed at light and electron microscopical levels. It was found that amalgam fillings (total, 0.7-1.2 g) caused deposition of mercury in the following tissues: spinal ganglia, anterior pituitary, adrenal, medulla, liver, kidneys, lungs, and intestinal lymph glands. In monkeys with maxillary silver amalgam implants (total, 0.1-0.3 g), mercury was found in the same organs except for liver, lungs, and intestinal lymph glands. Organs from the three control animals were devoid of precipitate. To evaluate whether silver released from the corroding amalgam fillings added to the staining pattern, tissue sections were exposed to potassium cyanide prior to being autometallographically developed. This treatment removes all traces of silver, leaving mercury sulfide accumulation untouched. By comparing sections that had been exposed to cyanide with untreated parallels no difference was seen in the pattern confirming that mercury was the only catalyst present in the tissue. These results strongly support what has been suggested previously that dental fillings in primates cause absorption of mercury released from amalgam fillings through lungs and intestinal tract, and that depending on exposure mercury is distributed to most organs and will eventually be found in the central nervous system. The present data also show that silver released from the corroding filling is not absorbed.
Exp Mol Pathol 1990 Jun
PMID:Traces of mercury in organs from primates with amalgam fillings. 211 6

Using specific monooxygenase and oxidase inhibitors in a plant cell/microbe coincubation assay, the biochemical mechanisms of the plant activation of two aromatic amines were compared. The biological endpoints included mutation induction, inhibition of mutagenicity, viability of the plant cells (activating system), and viability of the microbial cells (genetic indicator organism). The activation of m-phenylenediamine by TX1 cells was mediated by enzyme systems that were inhibited by diethyldithiocarbamate, potassium cyanide, methimazole, (+)-catechin or acetaminophen. The inhibition by metyrapone was attended by toxicity in the plant cells. These data implicate a TX1 cell peroxidase and a FAD-dependent monooxygenase in the plant activation of m-phenylenediamine. The TX1 cell activation of 2-aminofluorene was inhibited by diethyldithiocarbamate, 7,8-benzoflavone, acetaminophen or (+)-catechin. An additional pathway of the plant cells in the activation of 2-aminofluorene may involve a cytochrome P-448-type N-hydroxylase.
Environ Mol Mutagen 1990
PMID:The biochemical mechanisms of the plant activation of promutagenic aromatic amines. 216 71

The reaction of cyanide metmyoglobin with dithionite conforms to a two-step sequential mechanism with formation of an unstable intermediate, identified as cyanide bound ferrous myoglobin. This reaction was investigated by stopped-flow time resolved spectroscopy using different myoglobins, i.e. those from horse heart, Aplysia limacina buccal muscle, and three recombinant derivatives of sperm whale skeletal muscle myoglobin (Mb) (the wild type and two mutants). The myoglobins from horse and sperm whale (wild type) have in the distal position (E7) a histidyl residue, which is missing in A. limacina Mb as well as the two sperm whale mutants (E7 His----Gly and E7 His----Val). All these proteins in the reduced form display an extremely low affinity for cyanide at pH less than 10. The differences in spectroscopy and kinetics of the ferrous cyanide complex of these myoglobins indicate a role of the distal pocket on the properties of the complex. The two mutants of sperm whale Mb are characterized by a rate constant for the decay of the unstable intermediate much faster than that of the wild type, at all pH values explored. Therefore, we envisage a specific role of the distal His (E7) in controlling the rate of cyanide dissociation and also find that this effect depends on the protonation of a single ionizable group, with pK = 7.2, attributed to the E7 imidazole ring. The results on A. limacina Mb, which displays the slowest rate of cyanide dissociation, suggests that a considerable stabilizing effect can be exerted by Arg E10 which, according to Bolognesi et al. (Bolognesi, M., Coda, A., Frigerio, F., Gatti, C., Ascenzi, P., and Brunori, M. (1990) J. Mol. Biol. 213, 621-625), interacts inside the pocket with fluoride bound to the ferric heme iron. A mechanism of control for the rate of dissociation of cyanide from ferrous myoglobin, involving protonation of the bound anion, is discussed.
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PMID:Transient spectroscopy of the reaction of cyanide with ferrous myoglobin. Effect of distal side residues. 222 52

The use of digitonin to permeabilize Leishmania mexicana mexicana, Leishmania agamae, and Crithidia fasciculata plasma membranes enabled us to study Ca2+ transport in situ. The present results show that the mitochondria of these trypanosomatids are able to build up and retain a membrane potential as indicated by a tetraphenylphosphonium-sensitive electrode. Ca2+ uptake caused membrane depolarization compatible with the existence of an electrogenically mediated Ca2+ transport mechanism in these mitochondria. Ca2+ uptake was partially inhibited by ruthenium red, almost totally inhibited by carbonyl cyanide p-trifluoromethoxyphenylhydrazone, and stimulated by inorganic phosphate. Large amounts of Ca2+ were retained by C. fasciculata mitochondria even after addition of thiols and NAD(P)H oxidants such as t-butylhydroperoxide and diamide. In contrast, Ca2+ was not retained in the matrix of Leishmania sp. mitochondria for long periods of time. In addition to the mitochondrial Ca2+ uptake, a vanadate-sensitive Ca2(+)-transporting system was also detectable in these trypanosomatids.
Mol Biochem Parasitol 1990 Aug
PMID:Ca2+ transport in digitonin-permeabilized trypanosomatids. 223 96

Menadione bisulfite is a hepatotoxicant that damages periportal regions of the lobule in perfused liver in an oxygen-dependent manner. The effect of ethanol on menadione bisulfite toxicity was examined in perfused rat liver. Addition of menadione bisulfite (3 mM) alone to the perfusate increased oxygen uptake by 20-30 mumols/g/hr. Lactate dehydrogenase was released into the effluent after 60 min of perfusion and reached values around 100 units/g/hr. Under these conditions, trypan blue was taken up exclusively in periportal regions of the liver lobule; 44% of periportal cells were stained. In the presence of ethanol, maximal increases in oxygen uptake due to menadione bisulfite were much larger (about 90 mumols/g/hr), and lactate dehydrogenase release occurred earlier and reached higher maximal values (330 units/g/hr). Trypan blue staining was also more extensive; 90% of periportal cells were stained. The effect of ethanol on menadione bisulfite-induced oxygen uptake required metabolism via alcohol dehydrogenase (ADH), because ethanol increased oxygen uptake due to menadione bisulfite from 44 to 81 mumols/g/hr in deermice with ADH but had no effect in deermice lacking ADH. Other agents that increase NADH (xylitol and 2-ethyl-1-hexanol) also potentiated the stimulation of oxygen uptake due to menadione bisulfite, suggesting that ethanol was working by increasing the NADH redox state. Cyanide abolished the increase in oxygen uptake due to menadione bisulfite, both in the absence and in the presence of ethanol, supporting the hypothesis that the effect of ethanol on menadione bisulfite-mediated oxygen uptake involves the mitochondrial respiratory chain. Further, the stimulation of oxygen uptake by menadione bisulfite in isolated mitochondria was enhanced when matrix NADH was increased by addition of beta-hydroxybutyrate. These data indicate that ethanol potentiates oxygen uptake and toxicity due to menadione bisulfite most likely by generation of NADH for redox cycling of this model quinone.
Mol Pharmacol 1990 Dec
PMID:Ethanol potentiates oxygen uptake and toxicity due to menadione bisulfite in perfused rat liver. 225 Jun 68

Leishmania braziliensis maintained very low (50 +/- 20 nM) intracellular concentrations of calcium ions under normal conditions, as shown by the fluorimetric indicator QUIN2. Digitonin-permeabilized cells liberated large amounts of calcium ions in the presence of the ionophore A23187, indicating the presence of a large intracellular reservoir for this ion. Given the extraordinary extension of the single giant mitochondrion of Kinetoplastida and the known capacity of mitochondria from other sources to accumulate calcium, we tested the capacity of this organelle to accumulate calcium ions in Leishmania. Coupled mitochondrial vesicles, five-fold enriched in succinate-cytochrome c oxidoreductase, were obtained from promastigotes by gentle grinding (45 s) with glass beads in hypertonic buffer solution, followed by differential centrifugation. These vesicles had a respiratory control ratio of 1.82 +/- 0.15, and two phosphorylation sites (sites II and III) using succinate as electron donor, and were capable of calcium uptake in the presence of several respiratory substrates; this uptake was enhanced in the presence of ADP and Pi and was blocked by classical electron transport inhibitors. Uncouplers such as carbonyl cyanide p-trifluoromethoxy-phenylhydrazone (FCCP) and the calcium ionophore A23187 released previously accumulated calcium ions, suggesting that the driving force for the calcium uptake by the vesicles is the respiratory generated electrochemical potential gradient of protons. A study of the affinity of this system for calcium showed that even at 90 microM free calcium, succinate-induced calcium uptake is not saturated while approaching a level of 200 nmol min-1 (mg protein)-1, indicating a low-affinity, large-capacity system.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Biochem Parasitol 1990 Feb
PMID:Ca2+ transport in isolated mitochondrial vesicles from Leishmania braziliensis promastigotes. 230 88


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