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:1.6.5.3 (complex I)
8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An NADH dehydrogenase possessing a specific activity 3-5 times that of membrane-bound enzyme was obtained by extraction of Acholeplasma laidlawii membranes with 9.0% ethanol at 43 degrees C. This dehydrogenase contained only trace amounts of iron (suggesting an uncoupled respiration), a flavin ratio of 1:2 FAD to FMN and 30-40% lipid. Its resistance to sedimentation is probably due to the high flotation density of the lipids. It efficiently utilized ferricyanide, menadione and dichlorophenol indophenol as electron acceptors, but not O2, ubiquinone Q10 or cytochrome c. Lineweaver-Burk plots of the dehydrogenase were altered to linear functions upon extraction with 9.0% ethanol. A secondary site of ferricyanide reduction could not be explained by the presence of cytochromes, which these membranes lack. In comparison to other respiratory chain-linked NADH dehydrogenases in cytochrome-containing respiratory chains, this dehydrogenase was characterized by similar Km's with ferricyanide, dichlorophenol indophenol, menadione as electron acceptors, but considerably smaller V's with ferricyanide, dichlorophenol indophenol, menadione as electron acceptors, and smaller specific activities. It was not stimulated or reactivated by the addition of FAD, FMN, Mg2+, cysteine or membrane lipids, and was less sensitive to respiratory inhibitors than unextracted enzyme. The ineffectiveness of ADP stimulation on O2 uptake, the insensitivity to oligomycin and the very low iron content of A. laidlawii membranes were considered in relation to conservation of energy by these cells. Some kinetic properties of the dehydrogenation, the uniquely high glycolipid content and apparently uncoupled respiration at Site I were noteworthy characteristics of this NADH dehydrogenase from the truncated respiratory chain of A. laidlawii.
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PMID:The reduced nicotinamide adenine dinucleotide "oxidase" of Acholeplasma laidlawii membranes. 17 76

Membrane vesicles of Escherichia coli prepared by osmotic lysis of lysozyme ethylenediaminetetracetate (EDTA) spheroplasts have approximately 60% of the total membrane-bound reduced nicotinamide adenine dinucleotide (NADH) dehydrogenase (ED 1.6.99.3) and Mg2+-adenosine triphosphatase (ATPase) (EC 3.6.1.3) activities exposed on the outer surface of the inner membrane. Absorption of these vesicles with antiserum prepared against the purified soluble Mg2+-ATPase resulted in agglutination of approximately 95% of the inner membrane vesicles, as determined by dehydrogenase activity, and about 50% of the total membrane protein. The unagglutinated vesicles lacked all dehydrogenase activity and may consist of outer membrane. Lysozyme-EDTA vesicles actively transported calcium ion, using either NADH or adenosine 5'-triphosphate (ATP) as energy source. However, neither D-lactate nor reduced phenazine methosulfate energized calcium uptake, suggesting that the observed calcium uptake was not due to a small population of everted vesicles. Transport of calcium driven by either NADH or ATP was inhibited by simultaneous addition of D-lactate or reduced phenazine methosulfate. Proline transport driven by D-lactate oxidation was inhibited by either NADH oxidation or ATP hydrolysis. These results suggest that the portion of the total population of vesicles capable of active transport, i.e., the inner membrane vesicles, are functionally a homogeneous population but cannot be categorized as either right-side-out or everted, since activities normally associated with only one side of the inner membrane can be found on both sides of the membrane of these vesicles. Moreover, the data indicate that oxidation of NADH or hydrolysis of ATP by externally localized NADH dehydrogenase or Mg2+-ATPase establishes a protonmotive force of the opposite polarity from that established through D-lactate oxidation.
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PMID:Functional mosaicism of membrane proteins in vesicles of Escherichia coli. 19 Feb 12

In isolated plant mitochondria the oxidation of both succinate and exogenous NADH responded in the expected manner to the addition of ADP or uncoupling agents, and the uncoupled rate of respiration was often in excess of the rate obtained in the presence of ADP. However, the oxidation of NAD+-linked substrates responded in a much more complex manner to the addition of ADP or uncoupling agents such as carbonyl cyanide p-trifluoromethoxyphenylhydrazone to mitochondria oxidizing pyruvate plus malate failed to result in a reliable stimulation; this uncoupled rate could be stimulated by adding AMP or ADP in the presence of oligomycin or bongkrekic acid. Spectrophometric measurements showed that the addition of AMP or ADP resulted in the simultaneous oxidation of endogenous nicotinamide nucleotide and the reduction of cytochrome b. ADP was only effective in bringing about these changes in redox state in the presence of Mg2+ whereas AMP did not require Mg2+. It was concluded that AMP activated the flow of electrons from endogenous nicotinamide nucleotide to cytochrome b, possible at the level of the internal NADH dehydrogenase.
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PMID:The activation of non-phosphorylating electron transport by adenine nucleotides in Jerusalem-artichoke (Helianthus tuberosus) mitochondria. 122 6

Chromomycin A3 is an antitumor antibiotic which blocks macromolecular synthesis via reversible interaction with DNA template only in the presence of divalent metal ions such as Mg2+. The role of Mg2+ in this antibiotic-DNA interaction is not well understood. We approached the problem in two steps via studies on the interaction of (i) chromomycin A3 and Mg2+ and (ii) chromomycin A3-Mg2+ complex(es) and DNA. Spectroscopic techniques such as absorption, fluorescence, and CD were employed for this purpose. The results could be summed up in two parts. Absorption, fluorescence, and CD spectra of the antibiotic change upon addition of Mg2+ due to complex formation between them. Analysis of the quantitative dependence of change in absorbance of chromomycin A3 (at 440 nm) upon input concentration of Mg2+ indicates formation of two types of complexes with different stoichiometries and formation constants. Trends in change of fluorescence and CD spectroscopic features of the antibiotic in the presence of Mg2+ at different concentrations further corroborate this result. The two complexes are referred to as complex I (with 1:1 stoichiometry in terms of chromomycin A3:Mg2+) and complex II (with 2:1 stoichiometry in terms of chromomycin A3:Mg2+), respectively, in future discussions. The interactions of these complexes with calf thymus DNA were examined to check whether they bind differently to the same DNA. Evaluation of binding parameters, intrinsic binding constants, and binding stoichiometry, by means of spectrophotometric and fluorescence titrations, shows that they are different. Distinctive spectroscopic features of complexes I and II, when they are bound to DNA, also support that they bind differently to the above DNA. Measurement of thermodynamic parameters characterizing their interactions with calf thymus DNA shows that complex I-DNA interaction is exothermic, in contrast to complex II-DNA interaction, which is endothermic. This feature implies a difference in the molecular nature of the interactions between the complexes and calf thymus DNA. These observations are novel and significant to understand the antitumor property of the antibiotic. They are also discussed to provide explanations for the earlier reports that in some cases appeared to be contradictory.
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PMID:Role of magnesium ion in the interaction between chromomycin A3 and DNA: binding of chromomycin A3-Mg2+ complexes with DNA. 155 Aug 24

Manganese is known to accumulate in mitochondria and in mitochondria-rich tissues in vivo. Although Ca2+ enhances mitochondrial Mn2+ uptake, ATP-bound Mn2+ is not sequestered by suspended rat brain mitochondria, and ATP binds Mn2+ even more tightly than it binds Mg2+. Physiological levels of the polyamine spermine enhanced 54 Mn2+ uptake at the low [Ca2+]s characteristic of unstimulated cells (approximately 100 nM). With succinate as substrate, Mn2+ inhibited oxygen consumption by suspensions of rat liver mitochondria after the addition of ADP but not after the addition of uncoupler. With glutamate/malate as substrate, Mn2+ inhibited ADP-stimulated respiration and also slightly inhibited uncoupler-stimulated respiration. State 4 (resting) respiration was unchanged in all cases, indicating that the inner membrane retained its impermeability to protons. These results suggest that Mn2+ was not oxidized and that it can interfere directly with oxidative phosphorylation, most likely by binding to the F1 ATPase. Mn2+ may also bind to the NADH dehydrogenase complex, but not strongly enough to affect electron transport in vivo. It is suggested that accumulation of manganese within the mitochondria of globus pallidus may help explain the distinctive pathology of manganism.
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PMID:Mn2+ sequestration by mitochondria and inhibition of oxidative phosphorylation. 163 87

Slow active/inactive transition of the membrane-bound mitochondrial NADH-ubiquinone reductase (Kotlyar, A.B. and Vinogradov, A.D. (1990) Biochim. Biophys. Acta 1019, 151-158) is sensitive to Ca2+ and other divalent cations. Millimolar concentrations of Ca2+ drastically reduce the rate of the turnover-dependent activation of NADH-ubiquinone reductase. When NADH oxidase, the rotenone-sensitive NADH-ubiquinone reductase or the succinate-supported delta mu H+-dependent NAD+ reduction were initiated by the deactivated enzyme preparations all the three activities were strongly inhibited by Ca2+; no sensitivity of these reactions to Ca2+ was observed when the assays were started by the activated enzyme preparations. The affinity of the deactivated enzyme to polyvalent cations was in the following order: Ni2+ greater than Co2+ greater than La3+ greater than Mn2+ greater than Ca2+ approximately Mg2+ greater than Ba2+. Monovalent metal cations had no effect on the slow turnover-dependent enzyme activation. The apparent affinity of the deactivated enzyme to Ca2+ was strongly pH-dependent. The KCa2+ values of 5.7 mM and 0.6 mM at pH 7.5 and 8.5 were determined from the presteady-state kinetics parameters. The spontaneous temperature-dependent deactivation of the enzyme was insensitive to Ca2+. Ca2+ increases the reactivity of the enzyme sulfhydryl group in the deactivated preparations towards N-ethylmaleimide. This effect was also used to quantitate Ca2+ affinity for the enzyme. The KCa2+ values of 1.2 mM and 0.4 mM at pH 8.0 and 9.0, respectively, were determined. The data obtained suggest that Ca2+ content in the mitochondrial matrix may play an important role in the control of NADH oxidation by the respiratory chain.
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PMID:Effect of Ca2+ ions on the slow active/inactive transition of the mitochondrial NADH-ubiquinone reductase. 173 7

The plasma membrane fraction of chicken osteoclasts was purified utilizing 20% continuous Percoll gradients. Biochemical marker enzyme analysis (ouabain-sensitive Na+,K(+)-ATPase and 5'-nucleotidase) indicated that plasma membrane enrichment was 11.87-fold and 7.25-fold, respectively, and contamination with mitochondria, endoplasmic reticulum, and lysosomes was low as determined by succinic dehydrogenase, NADH dehydrogenase, and N-acetylglucosaminidase activities, respectively. SDS latency of Na+,K(+)-ATPase and 5'-nucleotidase activities of the isolated plasma membranes revealed that 43-50% of vesicles were sealed, with 10-16% in the inside-out orientation, depending on the membrane fraction used. Electron microscopy confirmed the vesicular nature of the plasma membrane fraction. The plasma membrane Ca2(+)-ATPase had a high-affinity (KCa = 0.22 microM; Vmax = 0.16 mumol/mg per min) and a low-affinity (KCa = 148 microM; Vmax = 0.37 mumol/mg per min) component. Calmodulin (0.12 microM) had no effect on Ca2(+)-ATPase activity. However, trifluoperazine (0.1 mM), a calmodulin antagonist, strongly inhibited especially the high-affinity component of the enzyme. Vanadate and lanthanum also caused inhibition. In the presence of CDTA, a potent Ca2+ and Mg2+ chelating agent, high-affinity Ca2(+)-ATPase activity was abolished, indicating that trace Mg2+ was essential for activity. The Ca2(+)-ATPase substrate curve using ATP showed a high-affinity (Km = 12.3 microM; Vmax = 0.022 mumol/mg per min) and a low-affinity (Km = 43.8 microM; Vmax = 0.278 mumol/mg per min) component. These results demonstrate that osteoclasts have a plasma membrane Ca2(+)-ATPase with characteristics similar to the enzyme responsible for active calcium extrusion in other cells.
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PMID:Characterization of a Ca2(+)-ATPase in osteoclast plasma membrane. 214 47

There exists considerable controversy regarding membrane topography in vesicles derived by osmotic lysis of spheroplasts of Gram-negative bacteria. It has been reported by others that bee venom can be used to quantitate the portion of a heterogeneous vesicle population with an inside-out orientation by determining the degree of loss of crypticity of NADH dehydrogenase activity. We have demonstrated that a major component of bee venom, melittin, causes an increase in the activity of several different respiratory enzymes in isolated membrane vesicles of Paracoccus denitrificans. The degree of stimulation produced by melittin is dependent upon (i) the nature of the respiratory substrates, (ii) the pH, (iii) the presence of Mg2+, (iv) the melittin: membrane protein ratio, and (v) the growth history of the cells from which the membrane vesicles were derived. Melittin-induced enhancement of TMPD:ascorbate and cytochrome c oxidase activities cannot be accounted for by increased accessibility of nonpermeant substrate to the interior of the vesicle. The stimulatory effect of melittin may rely in part on its ability to alter the proton permeability of the membrane thereby abolishing respiratory control. Collectively these observations call into question the usefulness of bee venom melittin in quantitative analyses of membrane topography. These results are consistent with the postulated existence of a homogeneous vesicle population in which the topography of the NADH dehydrogenase is different from that of the intact cell.
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PMID:The use of bee venom melittin to assess the topography of membrane vesicles derived from Paracoccus denitrificans. 625 50

Treatment of M. lysodeikticus protoplasts with subtilisin or pronase did not affect their permeability and led to a digestion of 20--30% of protein. DS-Na electrophoresis of protoplast membranes resulted in disappearance of three protein bands. This suggests that the outer surface of M. lysodeikticus protoplasts contains three proteins other than respiratory chain enzymes, which are subjected to an attack by proteinases. Treatment of the M. lysodeikticus membranes, isolated by osmotic shock, with proteinases resulted in a digestion of 20--50% of protein. The factors preventing the interaction between the membrane components (e.g. decrease of Mg2+ concentration, ultrasound, KCl, EDTA and particularly detergents) favoured the proteolysis; however, the bulk of the proteins remained insensitive to the effect of proteinases. The membranes pretreated with DS-Na or chlorophorm--methanol mixture proved to be good substrates for proteinases. Treatment of the membrane fraction with proteolytic enzymes allowed to obtain some data on localization of respiratory chain enzymes in the membrane stroma of M. lysodeikticus. Thus, cytochrome c is localized nearer to the membrane surface than cytochromes a and b, while malate dehydrogenase is plunged deeper into the membrane stroma as compared to NADH dehydrogenase.
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PMID:[Proteolysis as an approach to the study of protein distribution in the membrane of Micrococcus lysodeikticus]. 699 76

Numerous observations strongly support the hypothesis that dopaminergic neurons could be particularly vulnerable to an impairment of their energetic metabolism. In order to demonstrate the existence of such a selective vulnerability, the toxic effects of rotenone, an inhibitor of complex I of the respiratory chain, and of glutamate, which is very likely involved in the neurotoxicity induced by an energetic stress, were analyzed on cultured mouse mesencephalic neurons. Toxicity toward dopaminergic and GABAergic neurons was compared by measuring the residual uptakes of dopamine and GABA. Exposure to 5 nM rotenone for 6 hr or to a low concentration of glutamate (100 microM) for 1 hr did not lead to a high selective toxic effect on dopaminergic neurons. In contrast, dopaminergic neurons were three times less resistant to the sequential exposure to rotenone and glutamate than GABAergic neurons. A particular resistance of mesencephalic GABAergic neurons to the synergistic toxic effects of rotenone and glutamate was ruled out since two other neuronal types, the striatal cholinergic and GABAergic neurons, displayed the same weak vulnerability as the mesencephalic GABAergic neurons. This selective toxic effect of glutamate on rotenone-pretreated dopaminergic neurons was blocked by either AMPA or NMDA receptor antagonists and mimicked by combined treatment with AMPA and NMDA, or by NMDA alone when the medium was deprived of Mg2+ ions. Moreover, this NMDA-selective neurotoxicity was critically dependent on the presence of a physiological extracellular sodium concentration, since the use of choline chloride instead of sodium chloride had a protective effect on dopaminergic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A selective toxicity toward cultured mesencephalic dopaminergic neurons is induced by the synergistic effects of energetic metabolism impairment and NMDA receptor activation. 766 76


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