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)

Abnormalities of mitochondrial energy metabolism may play a role in normal aging and certain neurodegenerative disorders. In this regard, complex I of the electron transport chain has received substantial attention, especially in Parkinson's disease. The conventional method for studying complex I has been quantitation of enzyme activity in homogenized tissue samples. To enhance the anatomic precision with which complex I can be examined, we developed an autoradiographic assay for the rotenone site of this enzyme. [3H]dihydrorotenone ([3H]DHR) binding is saturable (KD = 15-55 nM) and specific, and Hill slopes of 1 suggest a single population of binding sites. Nicotinamide adenine dinucleotide (NADH) enhances binding 4- to 80-fold in different brain regions (EC50 = 20-40 microM) by increasing the density of recognition sites (Bmax). Nicotinamide adenine dinucleotide phosphate also increases binding, but NAD+ does not. In skeletal muscle, heart, and kidney, binding was less affected by NADH. [3H]DHR binding is inhibited by rotenone (IC50 = 8-20 nM), meperidine (IC50 = 34-57 microM), amobarbitol (IC50 = 375-425 microM), and MPP+ (IC50 = 4-5 mM), consistent with the potencies of these compounds in inhibiting complex I activity. Binding is heterogeneously distributed in brain with the density in gray matter structures varying more than 10-fold. Lesion studies suggest that a substantial portion of binding is associated with nerve terminals. [3H]DHR autoradiography is the first quantitative method to examine complex I with a high degree of anatomic precision. This technique may help to clarify the potential role of complex I dysfunction in normal aging and disease.
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PMID:[3H]dihydrorotenone binding to NADH: ubiquinone reductase (complex I) of the electron transport chain: an autoradiographic study. 865 75

Based on the DNA sequence of its structural genes, clustered in the hnd operon, the NADP-reducing hydrogenase of Desulfovibrio fructosovorans is thought to be a heterotetrameric complex in which HndA and HndC constitute the NADP-reducing unit and HndD constitutes the hydrogenase unit, respectively. The weak representativity of the enzyme among cell proteins has prevented its purification. This paper discusses the purification and characterization of the HndA subunit of this unique tetrameric iron hydrogenase overproduced in Escherichia coli. The purified subunit contains 1.7 mol of non-heme iron and 1.7 mol of acid-labile sulfide/mol. EPR analysis of the reduced form of HndA indicates that it contains a single binuclear [2Fe-2S] cluster. This cluster exhibits a spectrum of rhombic symmetry with values of gx, gy, and gz equal to 1.915, 1.950, and 2. 000, respectively, and a midpoint redox potential of -395 mV. The UV-visible and EPR spectra of the [2Fe-2S] cluster indicate that HndA belongs to the [2Fe-2S] family typified by the Clostridium pasteurianum [2Fe-2S] ferredoxin. The C-terminal sequence of HndA shows 27% identity with the C-terminal sequence of the 25-kDa subunit of NADH: quinone oxidoreductase from Paracoccus denitrificans, 33% identity with the C-terminal sequence of the 24-kDa subunit from Bos taurus complex I, and 32% identity with the entire sequence of C. pasteurianum [2Fe-2S] ferredoxin. The four cysteine residues involved in HndA cluster binding have been tentatively identified on the basis of sequence identity considerations. Evidence of a HndA organization based on two independent structural domains is discussed.
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PMID:Purification and characterization of the HndA subunit of NADP-reducing hydrogenase from Desulfovibrio fructosovorans overproduced in Escherichia coli. 948 16

It has been shown that treatment of bovine mitochondrial complex I (NADH-ubiquinone oxidoreductase) with NADH or NADPH, but not with NAD or NADP, increases the susceptibility of a number of subunits to tryptic degradation. This increased susceptibility involved subunits that contain electron carriers, such as FMN and iron-sulfur clusters, as well as subunits that lack electron carriers. Results shown elsewhere on changes in the cross-linking pattern of complex I subunits when the enzyme was pretreated with NADH or NADPH (Belogrudov, G., and Hatefi, Y. (1994) Biochemistry 33, 4571-4576) also indicated that complex I undergoes extensive conformation changes when reduced by substrate. Furthermore, we had previously shown that in submitochondrial particles the affinity of complex I for NAD increases by >/=20-fold in electron transfer from succinate to NAD when the particles are energized by ATP hydrolysis. Together, these results suggest that energy coupling in complex I may involve protein conformation changes as a key step. In addition, it has been shown here that treatment of complex I with trypsin in the presence of NADPH, but not NADH or NAD(P), produced from the 39-kDa subunit a 33-kDa degradation product that resisted further hydrolysis. Like the 39-kDa subunit, the 33-kDa product bound to a NADP-agarose affinity column, and could be eluted with a buffer containing NADPH. It is possible that together with the acyl carrier protein of complex I the NADP(H)-binding 39-kDa subunit is involved in intramitochondrial fatty acid synthesis.
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PMID:Mitochondrial NADH-ubiquinone oxidoreductase (Complex I). Effect of substrates on the fragmentation of subunits by trypsin. 952 11

Chlorophyll fluorescence measurements were performed on osmotically lysed potato chloroplasts in order to characterize the reactions involved in the dark reduction of photosynthetic inter-system chain electron carriers. Addition of NADH or NADPH to lysed chloroplasts increased the chlorophyll fluorescence level measured in the presence of a non-actinic light until reaching Fmax, thus indicating an increase in the redox state of the plastoquinone (PQ) pool. The fluorescence increase was more pronounced when the experiment was carried out under anaerobic conditions and was about 50% higher when NADH rather than NADPH was used as an electron donor. The NAD(P)H-PQ oxidoreductase reaction was inhibited by diphenylene iodonium, N-ethylmaleimide and dicoumarol, but insensitive to rotenone, antimycin A and piericidin A. By comparing the substrate specificity and the inhibitor sensitivity of this reaction to the properties of spinach ferredoxin-NADP+-reductase (FNR), we infer that FNR is not involved in the NAD(P)H-PQ oxidoreductase activity and conclude to the participation of rotenone-insensitive NAD(P)H-PQ oxidoreductase. By measuring light-dependent oxygen uptake in the presence of DCMU, methyl viologen and NADH or NADPH as an electron donors, the electron flow rate through the NAD(P)H-PQ oxidoreductase is estimated to about 160 nmol O2 min-1 mg-1 chlorophyll. The nature of this enzyme is discussed in relation to the existence of a thylakoidal NADH dehydrogenase complex encoded by plastidial ndh genes. Copyright 1998 Elsevier Science B.V.
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PMID:Reduction of the plastoquinone pool by exogenous NADH and NADPH in higher plant chloroplasts. Characterization of a NAD(P)H-plastoquinone oxidoreductase activity 952 46

Barley (Hordeum vulgare L.) leaves were used to isolate and characterize the chloroplast NAD(P)H dehydrogenase complex. The stroma fraction and the thylakoid fraction solubilized with sodium deoxycholate were analyzed by native polyacrylamide gel electrophoresis, and the enzymes detected with NADH and nitroblue tetrazolium were electroeluted. The enzymes electroeluted from band S from the stroma fraction and from bands T1 (ET1) and T2 from the thylakoid fraction solubilized with sodium deoxycholate had ferredoxin-NADP oxidoreductase (FNR; EC 1.18.1.2) and NAD(P)H-FeCN oxidoreductase (NAD[P]H-FeCNR) activities. Their NADPH-FeCNR activities were inhibited by 2'-monophosphoadenosine-5'-diphosphoribose and by enzyme incubation with p-chloromercuriphenylsulfonic acid (p-CMPS), NADPH, and p-CMPS plus NADPH. They presented Michaelis constant NADPH values that were similar to those of FNRs from several sources. Their NADH-FeCNR activities, however, were not inhibited by 2'-monophosphoadenosine-5'-diphosphoribose but were weakly inhibited by enzyme incubation with NADH, p-CMPS, and p-CMPS plus NADH. We found that only ET1 contained two polypeptides of 29 and 35 kD, which reacted with the antibodies raised against the mitochondrial complex I TYKY subunit and the chloroplast ndhA gene product, respectively. However, all three enzymes contained two polypeptides of 35 and 53 kD, which reacted with the antibodies raised against barley FNR and the NADH-binding 51-kD polypeptide of the mitochondrial complex I, respectively. The results suggest that ET1 is the FNR-containing thylakoidal NAD(P)H dehydrogenase complex.
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PMID:Association of ferredoxin-NADP oxidoreductase with the chloroplastic pyridine nucleotide dehydrogenase complex in barley leaves 957 93

Inside-out submitochondrial particles from both potato tubers and pea leaves catalyze the transfer of hydride equivalents from NADPH to NAD(+) as monitored with a substrate-regenerating system. The NAD(+) analogue acetylpyridine adenine dinucleotide is also reduced by NADPH and incomplete inhibition by the complex I inhibitor diphenyleneiodonium (DPI) indicates that two enzymes are involved in this reaction. Gel-filtration chromatography of solubilized mitochondrial membrane complexes confirms that the DPI-sensitive TH activity is due to NADH-ubiquinone oxidoreductase (EC 1.6.5.3, complex I), whereas the DPI-insensitive activity is due to a separate enzyme eluting around 220 kDa. The DPI-insensitive TH activity is specific for the 4B proton on NADH, whereas there is no indication of a 4A-specific activity characteristic of a mammalian-type energy-linked TH. The DPI-insensitive TH may be similar to the soluble type of transhydrogenase found in, e.g., Pseudomonas. The presence of non-energy-linked TH activities directly coupling the matrix NAD(H) and NADP(H) pools will have important consequences for the regulation of NADP-linked processes in plant mitochondria.
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PMID:Two separate transhydrogenase activities are present in plant mitochondria. 1054 98

Direct photoaffinity labeling of purified bovine heart NADH:ubiquinone oxidoreductase (complex I) with 32P-labeled NAD(H), NADP(H) and ADP has shown that five polypeptides become labeled, with molecular masses of 51, 42, 39, 30, and 18-20 kDa. The 51 and the 30-kDa polypeptides were labeled with either [32P]NAD(H), [32P]NADP(H) or [beta-32P]ADP. The 42-kDa polypeptide was labeled with [32P]NAD(H) and to a small extent with [beta-32P]ADP. It was not labeled with [32P]NADP(H). The 39-kDa polypeptide was labeled with [32P]NADPH and to a small extent with [beta-32P]ADP. Our previous studies had shown that this subunit also binds NADP, but not NAD(H) [Yamaguchi, M., Belogrudov, G.I. & Hatefi, Y. (1998) J. Biol. Chem. 273, 8094-8098]. The 18-20-kDa polypeptide was labeled only with [32P]NADPH. Among these polypeptides, the 51-kDa subunit is known to contain FMN and a [4Fe-4S] cluster, and is the NAD(P)H-binding subunit of the primary dehydrogenase domain of complex I. The possible roles of the other nucleotide-binding subunits of complex I have been discussed.
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PMID:The multiple nicotinamide nucleotide-binding subunits of bovine heart mitochondrial NADH:ubiquinone oxidoreductase (complex I). 1063 2

Studies of respiration on glucose in procyclic Trypanosoma congolense in the presence of rotenone, antimycin, cyanide, salicylhydroxamic acid and malonate have indicated the presence of NADH dehydrogenase, cytochrome b-c1, cytochrome aa3, trypanosome alternate oxidase and NADH fumarate reductase/succinate dehydrogenase pathway that contributes electrons to coenzyme Q of the respiratory chain. The rotenone sensitive NADH dehydrogenase, the trypanosome alternate oxidase, and cytochrome aa3 accounted for 24.5 +/- 6.5, 36.2 +/- 4.2 and 54.1 +/- 5.5% respectively of the total respiration. Activities of lactate dehydrogenase, NAD(+)-linked malic enzyme and pyruvate kinase were less than 6 nanomoles/min/mg protein suggesting that they play a minor role in energy metabolism of the parasite. Phosphoenolpyruvate carboxykinase, pyruvate dehydrogenase, succinate dehydrogenase, NADP(+)-linked malic enzyme, NADH fumarate reductase, malate dehydrogenase, and alpha-ketoglutarate dehydrogenase and glycerol kinase on the other hand had specific activities greater than 60 nanomoles/min/mg protein. These enzyme activities could account for the production of pyruvate, acetate, succinate and glycerol. The results further show that the amount of glycerol produced was 35-48% of the combined total of pyruvate, acetate and succinate produced. It is apparent that some of the glycerol 3-phosphate produced in glycolysis in the presence of salicylhydroxamic acid is dephosphorylated to form glycerol while the rest is oxidised via cytochrome aa3 to form acetate, succinate and pyruvate.
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PMID:Pathways of glucose catabolism in procyclic Trypanosoma congolense. 1084 79

The PSI-F subunit of photosystem I is a transmembrane protein with a large lumenal domain. The role of PSI-F was investigated in Arabidopsis plants transformed with an antisense construct of the psaF cDNA. Several plant lines with reduced amounts of the PSI-F subunit were generated. Many of the transgenic plants died, apparently because they were unable to survive without the PSI-F subunit. Plants with 5% of PSI-F were capable of photoautotrophic growth but were much smaller than wild-type plants. The plants suffered severely under normal growth conditions but recovered somewhat in the dark indicating chronic photoinhibition. Photosystem I lacking PSI-F was less stable, and the stromal subunits PSI-C, PSI-D, and PSI-E were present in lower amounts than in wild type. The lack of PSI-F resulted in an inability of light-harvesting complex I-730 to transfer energy to the P700 reaction center. In thylakoids deficient in PSI-F, the steady state NADP(+) reduction rate was only 10% of the wild-type levels indicating a lower efficiency in oxidation of plastocyanin. Surprisingly, the lack of PSI-F also gave rise to disorganization of the thylakoids. The strict arrangement in grana and stroma lamellae was lost, and instead a network of elongated and distorted grana was observed.
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PMID:Down-regulation of the PSI-F subunit of photosystem I (PSI) in Arabidopsis thaliana. The PSI-F subunit is essential for photoautotrophic growth and contributes to antenna function. 1090 Jan 98

We have previously shown that in Nicotiana sylvestris cytoplasmic male-sterile (CMS) mutants where the mtDNA lacks the nad7 gene coding for a subunit of respiratory Complex I (NADH:ubiquinone oxidoreductase, EC 1.6.5.3), glycine (Gly) oxidation was lower than in the wild type and insensitive to rotenone, suggesting Complex I dysfunction. In contrast, the oxidation rate of exogenous NADH and the capacity of the cyanide-resistant respiration (AOX) were enhanced. Here we report that, in contrast to Gly, the rate of malate oxidation was not affected, but proceeded totally in a rotenone-insensitive pathway, strongly suggesting that survival of CMS plants depends on the activation of internal and external alternative NAD(P) H dehydrogenases and that Gly decarboxylase activity depends on Complex I functioning. A similar defect in Complex I activity and Gly oxidation was found in the NMS1 nuclear mutant, defective in the processing of the nad4 transcript, but alternative NAD(P) H dehydrogenases were less activated. In CMS and NMS1, the fraction of the AOX pathway was increased, as compared to wild type, associated with higher amounts of aox transcripts, AOX protein, and plant resistance to cyanide. Non-phosphorylating respiratory enzymes maintained normal in vivo respiration levels in both mutants, but photosynthesis was decreased, in correlation with lower leaf conductance, emphasizing mitochondrial control on photosynthesis.
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PMID:Complex I impairment, respiratory compensations, and photosynthetic decrease in nuclear and mitochondrial male sterile mutants of Nicotiana sylvestris. 1108 Mar


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