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)

Oxidation of exogenous NADH in mitochondria isolated from wild type and mi-1 mutant of Neurospora crassa decreases rapidly in vitro. In mi-1 mutant mitochondria the inactivation concerns the alternate pathway of oxidation whereas in the wild type it involves an unknown component of the respiratory chain. The activity of the primary NADH dehydrogenase is constant within the time of the experiments (2-4 h). NADH oxidase is not inactivated if oxygen is removed from the incubation medium by nitrogen bubbling. Succinate oxidase does not show any remarkable changes in activity within 2-3 h. In fresh mitochondria of the mi-1 mutant reduced ubiquinone is completely reoxidized by cytochrome oxidase but only 80% reoxidized by the alternate oxidase. In aged mitochondria of the mi-1 mutant in the presence of cyanide, ubiquinone is reduced to the level characteristic for fresh mitochondria in which respiration is completely inhibited by cyanide plus salicylhydroxamic acid. In these mitochondria the reoxidation of the reduced ubiquinone proceeds only via the cytochrome pathway. It is supposed that a labile component(s) of the respiratory chain present in the mi-1 mutant and the wild type mitochondria may, in mi-1 mutant, act as an alternate oxidase.
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PMID:Disappearance of the cyanide-insensitive pathway of oxidation in mitochondria of MI-1 mutant of Neurospora crassa in vitro. 20 34

Recent studies have shown that intrarectal administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) in ethanol or intramural injection of TNBS in saline produces an acute and possibly chronic colitis in rats. It has been assumed that interstitial TNBS initiates the inflammatory response via macrophage-mediated recognition and degradation of TNBS-modified mucosal cells and proteins. However, it is known that certain flavoproteins and/or reductants interact with compounds containing the nitro functional group to generate pro-inflammatory, nitrogen-centered free radicals and reactive oxygen metabolites. The objective of this study was to assess the ability of the rat colon, using either colon homogenates, isolated colonocytes, or intestinal interstitial fluid, to produce reactive oxygen species via enzymatic and/or nonenzymatic metabolism of TNBS. It was found that the addition of TNBS (1 mmol/L) to the 10,000 x g supernatant of rat colon homogenates increased the rate of superoxide production from normally undetectable levels to 2.6 +/- 0.23 nmol.min-1.mg protein-1. Addition of nicotinamide adenine dinucleotide, reduced form (NADH; 1 mmol/L) to colon homogenates containing TNBS significantly enhanced superoxide production to 10.4 +/- 0.9 nmol.min-1.mg-1. Similarly, addition of nicotinamide adenine dinucleotide phosphate, reduced form (NADPH; 1 mmol/L) to colon extracts containing TNBS produced an even further increase in the rate of superoxide formation to 25.2 +/- 1.1 nmol.min-1.mg-1. Addition of NADH or NADPH to the colon homogenate in the absence of TNBS produced no detectable superoxide formation, suggesting that TNBS was required for the enhanced oxidative metabolism. In a separate series of experiments, it was found that isolated colonocytes produced small but significant amounts of superoxide (3.15 +/- 0.6 nmol/2 x 10(6) cells) that were significantly increased in the presence of ethanol to 6.55 +/- 1.14 nmol/2 x 10(6) cells. Using purified preparations of two flavoproteins found in the rat colon, it was shown that the addition of TNBS (1 mmol/L) to purified NADH dehydrogenase or glutathione reductase increased the rate of superoxide formation by these enzymes from normally undetectable levels to 1.6 nmol/min and 1.2 nmol/min, respectively. In addition, it was found that intestinal interstitial fluid (lymph) initiated redox cycling of TNBS such that 28.1 +/- 1.6 nmol of oxygen was consumed per minute per milliliter of lymph. This increase in oxygen consumption was inhibited by the addition of superoxide dismutase and catalase. One possible metabolite involved in both mucosal and lymph-mediated metabolism of TNBS is ascorbic acid.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Metabolism of trinitrobenzene sulfonic acid by the rat colon produces reactive oxygen species. 164 28

The respiration chain in the membranes of whole Actinomyces roseoflavus (var. roseofungini) cells from the parent and secondary cultures is sensitive to KCN, non-sensitive to Triton X-100 treatment removing the antibiotic roseofungin from the cells, and has a very high for the bacteria respiration control. When the cells are in contact with atomic tritium at the temperature of liquid nitrogen, roseofungin is tritiated and binds to A. roseoflavus isolated membranes and whole cells, mostly to those of the parent culture as compared to the secondary culture. A fraction of membranes which lost NADH dehydrogenase in the course++ of purification was isolated from the cells disintegrated in the frozen state.
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PMID:[Comparative study of different variants of Actinomyces roseoflavus producing the polyene antibiotic roseofungin]. 321 Oct 8

Pd(II) complexes of two anthracyclines, adriamycin and daunorubicin, have been studied. Using potentiometric absorption, fluorescence, and circular dichroism measurements, we have shown that adriamycin can form two complexes with Pd(II). The first complex (I) involves two molecules of drug per Pd(II) ion; one of the molecules is chelated to Pd(II) through the carbonyl oxygen on C12 and the phenolate oxygen on C11, and the other one is bound to Pd(II) through the nitrogen of the amino sugar. This complexation induces a stacking of the two molecules of drug. In the second complex (II), two Pd(II) ions are bound to two molecules of drug (A1 and A2). One Pd(II) is bound to the oxygen on the carbons C11 and C12 of molecule A1 and the amino sugar of molecule A2 whereas the second Pd(II) ion is bound to the oxygen on C11 and C12 of molecule A2 and the amino sugar of molecule A1. The same complexes are formed between Pd(II) and daunorubicin. The stability constant for complex II is beta = (1.3 +/- 0.5) X 10(22). Interaction with DNA has been studied, showing that almost no modification of the complex occurred. This complex displays antitumor activity against P-388 leukemia that compares with that of the free drug. Complex II, unlike adriamycin, does not catalyze the flow of electrons from NADH to molecular oxygen through NADH dehydrogenase.
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PMID:Metal anthracycline complexes as a new class of anthracycline derivatives. Pd(II)-adriamycin and Pd(II)-daunorubicin complexes: physicochemical characteristics and antitumor activity. 396 54

1. Plasma membranes were isolated from Krebs II ascite cells grown in the mouse. Cells were disrupted by nitrogen cavitation in an isotonic alkaline buffer containing magnesium and ATP. Isolation was performed in an alkaline-buffered self-generating gradient of Percoll with an angular rotor. At each step of the preparation, the pH appeared as the critical aspect of our procedure. 2. External membrane markers were concanavalin A and 5'-nucleotidase (EC 3.1.3.5). They reached a relative specific activity of 10, whereas this value was only of 0.7 for the endoplasmic reticulum marker, NADH dehydrogenase (EC 1.6.99.3). 3. Plasma membrane from 4 ml packed cells were isolated within 1 h after homogenization with good yield: 50% and 67% of total [3H]concanavalin A and 5'-nucleotidase, respectively, were recovered in the two plasma membrane fractions. 4. Electron microscopy examination showed the presence of vesicles of different sizes devoid of other structural contaminants. 5. Using the specific binding of concanavalin A to the external cell membrane, it was calculated that about 50% of the total cell phospholipid and 10% protein are located in the plasma membrane. Their sphingomyelin content is much higher than in the whole cell, in contrast to phosphatidylinositol, known as a more specific endoplasmic reticulum phospholipid.
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PMID:Isolation and characterization of plasma membranes from krebs II ascite cells using Percoll gradient. 628 35

The NIT2 nitrogen regulatory protein of Neurospora is a DNA binding protein which contains a single Cys2/Cys2 type finger motif followed immediately by a highly basic region. Several different approaches were employed to identify nucleotides which appear to be in contact with NIT2 in the DNA-protein complex. Methylation interference and missing contact analyses with the promoter DNA fragment of the L-amino acid oxidase gene showed that all three purines in both of two GATA core sequences and the single adenine residue in each of the complementary TATC sequences were in intimate contact with NIT2. Modification or loss of the three purine residues located between the two GATA core sequences also significantly reduced NIT2 binding, whereas alteration of purines which flank the binding element showed only minor effects. Chemical modification of all six thymine bases in the two GATA and TATC complement core sequences also strongly affected NIT2 binding. High affinity NIT2 binding sites appear to contain at least two GATA core sequences, with single GATA sequences acting only as weak binding sites. Mobility shift experiments with the DNA fragment upstream of nit-3, the structural gene for nitrate reductase, revealed two DNA-NIT2 protein complexes. In complex I, which is formed first, NIT2 was bound to a pair of GATA sites located at -180. In complex II, the paired GATA sites at -180 plus a single GATA site at -290 were all occupied by NIT2. A DNA fragment containing only the single -290 GATA element bound NIT2 very weakly. The affinity of this single GATA for NIT2 was ten to twenty times greater when it was situated on the same DNA fragment with the distant paired GATA elements than when alone.
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PMID:Recognition of specific nucleotide bases and cooperative DNA binding by the trans-acting nitrogen regulatory protein NIT2 of Neurospora crassa. 839 61

Isoquinoline derivatives exert 1-methyl-4-phenylpyridinium (MPP+)-like activity as inhibitors of complex I and alpha-ketoglutarate dehydrogenase activity in rat brain mitochondrial fragments. We now examine the ability of 19 isoquinoline derivatives and MPP+ to accumulate and inhibit respiration in intact rat liver mitochondria, assessed using polarographic techniques. None of the compounds examined inhibited respiration supported by either succinate + rotenone or tetramethylparaphenylenediamine (TMPD) + ascorbate. However, with glutamate + malate as substrates, 15 isoquinoline derivatives and MPP+ inhibited state 3 and, to a lesser extent, state 4 respiration in a time-dependent manner. None of the isoquinoline derivatives were more potent than MPP+. 6,7-Dimethoxy-1-styryl-3,4-dihydroisoquinoline uncoupled mitochondrial respiration. Qualitative structure-activity relationship studies revealed that isoquinolinium cations were more active than isoquinolines in inhibiting mitochondrial respiration; these, in turn, were more active than dihydroisoquinolines and 1,2,3,4-tetrahydroisoquinolines. Three-dimensional quantitative structure-activity relationship studies using Comparative Molecular Field Analysis showed that the inhibitory potency of isoquinoline derivatives was determined by steric, rather than electrostatic, properties of the compounds. A hypothetical binding site was identified that may be related to a rate-limiting transport process, rather than to enzyme inhibition. In conclusion, isoquinoline derivatives are less potent in inhibiting respiration in intact mitochondria than impairing complex I activity in mitochondrial fragments. This suggests that isoquinoline derivatives are not accumulated by mitochondria as avidly as MPP+. The activity of charged and neutral isoquinoline derivatives implicates both active and passive processes by which these compounds enter mitochondria, although the quaternary nitrogen moiety of the isoquinolinium cations favours mitochondrial accumulation and inhibition of respiration. These findings suggest that isoquinoline derivatives may exert mitochondrial toxicity in vivo similar to that of MPTP/MPP+.
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PMID:Effects of isoquinoline derivatives structurally related to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on mitochondrial respiration. 863 91

The activities of NAD+-photoreduction and NADH/decyl-ubiquinone reductase in membrane preparations of Rhodobacter capsulatus changed to the same extent under different conditions. These results indicated that NADH:ubiquinone oxidoreductase (complex I) catalyzes the electron transport in the downhill direction (respiratory chain) and in the uphill direction (reverted electron flow). This conclusion was confirmed by the characterization of a complex-I-deficient mutant of R. capsulatus. The mutant was not able to reduce NAD+ in the light. Since this mutant was not able to grow photoautotrophically, we concluded that complex I is the enzyme that catalyzes the reverted electron flow to NAD+ to provide reduction equivalents for CO2 fixation. Complex I is not essential for the reverted electron flow to nitrogenase since the mutant grew under nitrogen-fixing conditions. As shown by immunological means, NuoE, a subunit of complex I from R. capsulatus having an extended C-terminus, was modified depending on the nitrogen source present in the growth medium. When the organism used N2 instead of NH4+, a smaller NuoE polypeptide was synthesized. The complex-I-deficient mutant was not able to modify NuoE. The function of the modification is discussed.
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PMID:Complex I of Rhodobacter capsulatus and its role in reverted electron transport. 944 80

The rnf genes of Rhodobacter capsulatus, essential for nitrogen fixation, are thought to encode a system for electron transport to nitrogenase. In the present study, we have attempted to overexpress the rnf genes in Escherichia coli to investigate the molecular properties of the corresponding proteins. Corrections were made to the published DNA sequence of the rnf operon, resulting in the identification of two genes, rnfG and rnfH. The rnfABCDGEH operon thus comprises seven genes and shows similarities in gene arrangement and deduced protein sequences to homologous regions in the genomes of Haemophilus influenzae and E. coli. Four of the rnf gene products were found to be similar in sequence to components of an Na+-dependent NADH:ubiquinone oxidoreductase from Vibrio alginolyticus. Three of the rnf genes were successfully overexpressed in E. coli as His-tagged polypeptides, whereas the products of rnfA, rnfD and rnfE, predicted to be transmembrane proteins, could not be stably maintained in E. coli. The rnfB and rnfC gene products were isolated as two brown proteins with apparent molecular-mass values of 25 kDa and 55 kDa, respectively. RnfB was shown to contain one [2Fe-2S] cluster, based on absorption spectrophotometry, EPR spectroscopy and iron content. Recombinant RnfC contained at least one iron-sulfur cluster, most likely of the [4Fe-4S] type. Unambiguous identification of the prosthetic groups was, however, precluded by the extreme instability of this protein. In R. capsulatus, RnfB and RnfC were found by immunoblot analysis to be tightly bound to the membrane, despite their hydrophilic character. The RnfB and RnfC proteins were absent in mutant strains bearing insertions at various positions within the rnfABCDGEH operon, suggesting that their stability depends on the cosynthesis of the other rnf gene products. We observed that iron limitation during growth resulted in a decrease both in the cellular content of RnfB and in the level of transcription of the rnfABCDGEH operon, indicating that the expression of this operon is regulated as a function of iron availability.
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PMID:Overexpression in Escherichia coli of the rnf genes from Rhodobacter capsulatus--characterization of two membrane-bound iron-sulfur proteins. 949 68

Dual binding sites for pyridinium-type inhibitors in bovine heart mitochondrial complex I have been proposed (Gluck, M. R., Krueger, M. J., Ramsay, R. R., Sablin, S. O., Singer, T. P., and Nicklas, W. J. (1994) J. Biol. Chem. 269, 3167-3174). The marked biphasic nature of the dose-response curve for inhibition of the enzyme by MP-6(N-methyl-4-[2-(p-tert-butylbenzyl)propyl]pyridinium) makes this compound the first selective inhibitor of the two sites (Miyoshi, H., Inoue, M., Okamoto, S., Ohshima, M., Sakamoto, K., and Iwamura, H. (1997) J. Biol. Chem. 272, 16176-16183). Modifications of the structure of MP-6 show that a tert-butyl group on the benzene ring, a methyl group attached to the pyridine nitrogen atom, para-substitution pattern in the pyridine ring, and the presence of a branched structure in the spacer moiety are important for the selective inhibition. On the basis of the structural specificity, we synthesized a selective inhibitor, MP-24 (N-methyl-4-[2-methyl-2-(p-tert-butylbenzyl)propyl]pyridinium), which elicits greater selectivity. Characterization of the inhibitory behavior of MP-24 provided further strong evidence for the dual binding sites model.
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PMID:Specificity of pyridinium inhibitors of the ubiquinone reduction sites in mitochondrial complex I. 965 20


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