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)

Mitochondrial NADH:ubiquinone oxidoreductase (complex I) is the most complicated enzyme in the respiratory chain and is composed of at least 26 distinct polypeptides. Two hydrophilic subfractions of bovine heart complex I were systematically resolved into individual polypeptides by chromatography. Three polypeptides (51, 24, and 9 kDa) were isolated from the flavoprotein fraction (FP) of complex I, and the complete amino acid sequence of the 9 kDa polypeptide was determined. The 9 kDa polypeptide is composed of 75 amino acids with a molecular weight of 8,437. This protein exhibits no obvious sequence similarity to other proteins. The iron-sulfur protein fraction (IP) of complex I was separated into eight polypeptides, 75, 49, 30, 20, 18, 15, 13 kDa-A, and 13 kDa-B. The 20 kDa polypeptide was recognized as a novel component of IP for the first time. The N-terminal and several peptide sequences of the 20 kDa polypeptide were determined. Comparison of the sequences revealed significant sequence similarities of the 20 kDa polypeptide to the psbG gene products encoded in the chloroplast genome. The conserved sequence in these proteins was also found in the small subunit of the nickel-containing hydrogenases. These results suggest that complex I is related to other redox enzyme complexes.
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PMID:The amino acid sequence of the 9 kDa polypeptide and partial amino acid sequence of the 20 kDa polypeptide of mitochondrial NADH:ubiquinone oxidoreductase. 177 79

Purified ubiquinol-cytochrome c reductase of beef heart mitochondria is very stable in aqueous solution; it suffers little damage upon illumination with visible light under aerobic or anaerobic conditions. However, it is rapidly inactivated when the photosensitizer hematoporphyrin is present during illumination. The hematoporphyrin-promoted photoactivation is dependent on sensitizer dose, illumination time, and oxygen. Singlet oxygen is shown to be the destructive agent in this system. The photoinactivation of ubiquinol-cytochrome c reductase is prevented by excess exogenous ubiquinone, regardless of its redox state. This protective effect is not due to protein-ubiquinone interactions but to the singlet oxygen scavenger property of ubiquinone. Ubiquinone also protects against hematoporphyrin-promoted photoinactivation of succinate-ubiquinone reductase and cytochrome c oxidase. The photoinactivation site in ubiquinol-cytochrome c reductase is the iron-sulfur cluster of Rieske's protein. Two histidine residues, presumably serving as two ligands for the iron-sulfur cluster of Rieske's protein, are destroyed. No polypeptide bond cleavage is detected. Photoinactivation has little effect on the spectral properties of cytochromes b and c1 but alters their reduction rates substantially. this photoinactivation also causes the formation of proton-leaking channels in the complex. When the photoinactivated reductase is co-inlaid with intact ubiquinol-cytochrome c reductase or cytochrome c oxidase in a phospholipid vesicle, no proton ejection can be detected during the oxidation of their corresponding substrates.
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PMID:Hematoporphyrin-promoted photoinactivation of mitochondrial ubiquinol-cytochrome c reductase: selective destruction of the histidine ligands of the iron-sulfur cluster and protective effect of ubiquinone. 184 89

1. In primary biliary cirrhosis, the major M2 autoantigen, reacting with antimitochondrial antibodies in sera from greater than 90% of patients, has been identified as the E2 component of the pyruvate dehydrogenase complex. However, two recent reports suggest that alternative polypeptides may be major autoantigens. 2. The evidence that a 75 kDa subunit of complex I of the respiratory chain is a major autoantigen (Frostell, Mendel-Hartvig, Nelson, Totterman, Bjorkland & Ragan, Scand. J. Immunol. 1988; 28, 157-65) is refuted. The findings of Frostell et al. can be explained by contamination of complex I with the pyruvate dehydrogenase complex, evidence for which is presented here. 3. Inspection of the partial amino acid sequence of an unidentified mitochondrial autoantigen (Muno, Kominami, Ishii, Usui, Saituku, Sakakibara & Namihisa, Hepatology 1990; 11, 16-23) shows that it is the E1 beta-subunit of the pyruvate dehydrogenase complex, previously identified as a major autoantigen, and not a 'new' alternative major autoantigen. 4. These findings substantiate previous work showing that the mitochondrial M2 autoantigens identified so far in primary biliary cirrhosis are all polypeptide components of the pyruvate dehydrogenase complex or the other related 2-oxo acid dehydrogenase complexes.
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PMID:Clarification of the identity of the major M2 autoantigen in primary biliary cirrhosis. 185 84

The light-harvesting complex I (LHI) of Rhodobacter capsulatus is an oligomer of basic subunits each consisting of the two different pigment-binding polypeptides LHI alpha and LHI beta, encoded by the pufA (LHI alpha) and pufB (LHI beta) genes. Pulse-labeling experiments showed that in the presence of the LHI alpha polypeptide, the LHI beta polypeptide was inserted earlier into the intracytoplasmic membrane than was the LHI alpha polypeptide. Each of the pufA and pufB genes was deleted to test whether the LHI alpha and beta polypeptides, respectively, are inserted into the intracytoplasmic membrane independently of the LHI partner polypeptide. Neither deletion mutant strain formed the LHI antenna, but a functional reaction center complex was present. Pulse-labeling experiments indicated that the LHI beta polypeptide was inserted into the intracytoplasmic membrane with the same kinetics and in the same amounts regardless of whether the LHI alpha polypeptide was present. However, the LHI beta polypeptide did not accumulate in the membrane in the absence of the LHI alpha protein but was degraded linearly within about 12 min. In contrast to the LHI beta protein, only trace amounts of the LHI alpha polypeptide were inserted into or attached to the membrane if the LHI beta polypeptide was not synthesized.
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PMID:Incorporation of light-harvesting complex I alpha and beta polypeptides into the intracytoplasmic membrane of Rhodobacter capsulatus. 188 14

The chloroplast genomes of Marchantia polymorpha, Nicotiana tabacum, and Oryza sativa contain open reading frames (ORFs or potential genes) encoding homologues of some of the subunits of mitochondrial NADH:ubiquinone oxidoreductase (complex I). Seven of these subunits (ND1-ND4, ND4L, ND5, and ND6) are products of the mitochondrial genome, and two others (the 49- and 30-kDa components of the iron-sulfur protein fraction) are nuclear gene products. These findings have been taken to indicate the presence in chloroplasts of an enzyme related to complex I, possibly an NAD(P)H:plastoquinone oxidoreductase, participating in chlororespiration. This view is reinforced by the present work in which we have shown that chloroplast genomes encode a homologue of the 23-kDa subunit, another nuclear-encoded component of bovine complex I. The 23-kDa subunit is in the hydrophobic protein fraction of the enzyme, the residuum after removal of the flavoprotein and iron-sulfur protein fractions. The sequence motif CysXXCysXXCysXXXCysPro, which provides ligands for tetranuclear iron-sulfur centers in ferredoxins, occurs twice in its polypeptide chain and is evidence of two associated 4Fe-4S clusters. This is the only iron-sulfur protein identified so far in the hydrophobic protein fraction of complex I, and so it is possible that one of these centers is that known as N-2, the donor of electrons to ubiquinone. The sequence of the 23-kDa subunit is closely related to potential proteins, which also contain the cysteine-rich sequence motifs, encoded in the frxB ORFs in chloroplast genomes.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A homologue of a nuclear-coded iron-sulfur protein subunit of bovine mitochondrial complex I is encoded in chloroplast genomes. 190 Oct 22

The NADH dehydrogenase complex isolated from Paracoccus denitrificans is composed of approximately 10 unlike polypeptides and contains noncovalently bound FMN, non-heme iron, and acid-labile sulfide [Yagi, T. (1986) Arch. Biochem. Biophys. 250, 302-311]. The NADH-binding subunit (Mr = 50,000) of this enzyme complex was identified by direct photoaffinity labeling with [32P]NADH [Yagi, T., & Dinh, T.M. (1990) Biochemistry 29, 5515-5520]. Primers were synthesized on the basis of the N-terminal amino acid sequence of this polypeptide, and these primers were used to synthesize an oligonucleotide probe by the polymerase chain reaction. This probe was utilized to isolate the gene encoding the NADH-binding subunit from a genomic library of P. denitrificans. The nucleotide sequence of the gene and the deduced amino acid sequence of the entire NADH-binding subunit were determined. The NADH-binding subunit has 431 amino acid residues and a calculated molecular weight of 47,191. The encoded protein contains a putative NAD(H)-binding and an iron-sulfur cluster-binding consensus sequence. The deduced amino acid sequence of the Paracoccus NADH-binding subunit shows remarkable similarity to the alpha subunit of the NAD-linked hydrogenase of Alcaligenes eutrophus H16. When partial DNA sequencing of the regions surrounding the gene encoding the NADH-binding subunit was carried out, sequences homologous to the 24-, 49-, and 75-kDa polypeptides of bovine complex I were detected, suggesting that the structural genes of the Paracoccus NADH dehydrogenase complex constitute a gene cluster.
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PMID:The NADH-binding subunit of the energy-transducing NADH-ubiquinone oxidoreductase of Paracoccus denitrificans: gene cloning and deduced primary structure. 190 52

Mitochondrial NADH:ubiquinone oxidoreductase (complex I) is the most complicated system in the respiratory chain. It consists of many subunits, some of which hold iron-sulfur clusters, but structural information is still limited. The amino acid sequences of two 13 kDa polypeptides, 13 kDa-A and 13 kDa-B polypeptides, of iron-sulfur protein fraction (IP) of bovine heart mitochondrial complex I were determined by a combination of protease digestion, Edman degradation, and carboxypeptidase digestion. The 13 kDa-A polypeptide was composed of 96 amino acids with a molecular weight of 10,536. The 13 kDa-B polypeptide consisted of 114 amino acids and had an acetylated amino terminus. The molecular weight of this protein was calculated to be 13,130 including the acetyl group. These proteins had no obvious sequence similarity to other known proteins. The partial amino acid sequence of 30 kDa-B polypeptide of IP was also determined to reveal a characteristic arrangement of cysteine residues that could be involved in iron-sulfur cluster formation.
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PMID:The amino acid sequences of two 13 kDa polypeptides and partial amino acid sequence of 30 kDa polypeptide of complex I from bovine heart mitochondria: possible location of iron-sulfur clusters. 190 66

The NADH dehydrogenase complex isolated from Paracoccus denitrificans is composed of approximately 10 unlike polypeptides [Yagi, T. (1986) Arch. Biochem. Biophys. 250, 302-311]. Structural genes encoding the subunits of this enzyme complex constitute at least one gene cluster [Xu, X., Matsuno-Yagi, A., & Yagi, T. (1991) Biochemistry 30, 6422-6428]. The 25-kDa subunit (NQO2), which has been isolated from sodium dodecyl sulfate-polyacrylamide gels, is a polypeptide of this enzyme complex. The partial N-terminal amino acid sequence and amino acid composition of the NQO2 subunit have been determined. On the basis of the amino acid sequence, the NQO2 gene was found to be located 1.7 kilobase pairs upstream of the gene for NADH-binding subunit (NQO1). The complete nucleotide sequence of the NQO2 gene was determined. It is composed of 717 base pairs and codes for 239 amino acid residues with a calculated molecular weight of 26,122. The NQO2 subunit is homologous to the Mr 24,000 subunit of the mammalian mitochondrial NADH-ubiquinone oxidoreductase which bears an electron paramagnetic resonance-visible binuclear iron-sulfur cluster (probably cluster N1b). Comparison of the predicted amino acid sequence of the Paracoccus NQO2 subunit with those of its mammalian counterparts suggests putative binding sites for the iron-sulfur cluster. In addition, nucleotide sequencing shows the presence of two unidentified reading frames between the NQO1 and NQO2 genes. These are designated URF1 and URF2 and are composed of 261 and 642 base pairs, respectively. The possible function of the protein coded for the URF2 is discussed.
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PMID:Characterization of the 25-kilodalton subunit of the energy-transducing NADH-ubiquinone oxidoreductase of Paracoccus denitrificans: sequence similarity to the 24-kilodalton subunit of the flavoprotein fraction of mammalian complex I. 190 71

The gene encoding NADH dehydrogenase from an alkalophile, Bacillus sp., was cloned and sequenced. The cloned DNA fragment contained an open reading frame of 1,557 nucleotides which encodes a polypeptide composed of 519 amino acid residues (Mr 55,830). The predicted amino acid sequence was consistent with the partial amino acid sequences including the N-terminal and C-terminal sequences determined in a previous study. Sequence comparison with other flavoenzymes revealed high homology between the present dehydrogenase and Escherichia coli thioredoxin reductase.
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PMID:Nucleotide sequence of the gene encoding NADH dehydrogenase from an alkalophile, Bacillus sp. strain YN-1. 191 90

The arrangement of the large (70,000-Mr) and small (30,000-Mr) subunits of succinate dehydrogenase in the mitochondrial inner membrane was investigated by immunoblot analysis of bovine heart mitochondria (right-side-out, outer membrane disrupted) or submitochondrial particles (inside-out) that had been subjected to surface-specific proteolysis. Both subunits were resistant to proteinase treatment provided that the integrity of the inner membrane was preserved, suggesting that neither subunit is exposed at the cytoplasmic surface of the membrane. The bulk of the small subunit appears to protrude into the matrix compartment, since the 30,000-Mr polypeptide is degraded extensively during limited proteolysis of submitochondrial particles without the appearance of an immunologically reactive membrane-associated fragment: moreover, a soluble 27,000-Mr peptide derived from this subunit is observed transiently on incubation with trypsin. Similar data obtained from the large subunit suggest that this polypeptide interacts with the matrix side of the inner membrane via two distinct domains; these are detected as stable membrane-associated fragments of 32,000 Mr and 27,000 Mr after treatment of submitochondrial particles with papain or proteinase K, although the 27,000-Mr fragment can be degraded further to low-Mr peptides with trypsin or alpha-chymotrypsin. A stable 32,000-34,000-Mr fragment is generated by a variety of specific and non-specific proteinases, indicating that it may be embedded largely within the lipid bilayer, or is inaccessible to proteolytic attack owing to its proximity to the surface of the intact membrane, possibly interacting with the hydrophobic membrane anchoring polypeptides of the succinate: ubiquinone reductase complex.
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PMID:Topography of succinate dehydrogenase in the mitochondrial inner membrane. A study using limited proteolysis and immunoblotting. 199 68


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