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A B Kotlyar M Gutman B A Ackrell 《Biochemical and biophysical research communications》1992,186(3):1656-1662
Two new methods have been devised for measuring fumarate reduction by beef heart succinate-ubiquinone oxidoreductase with quinols as electron donors. In one assay the quinone is maintained in the reduced state by coupling fumarate reduction with the DT-diaphorase reaction, in the other assay by the presence of excess dithionite. The advantages of these methods are discussed, along with preliminary characterization of the quinol-protein interaction. 相似文献
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Tomitsuka E Hirawake H Goto Y Taniwaki M Harada S Kita K 《Journal of biochemistry》2003,134(2):191-195
Succinate-ubiquinone reductase (complex II) is an important enzyme complex in both the tricarboxylic acid cycle and aerobic respiration. A recent study showed that defects in human complex II are associated with cancers as well as mitochondrial diseases. Mutations in the four subunits of human complex II are associated with a wide spectrum of clinical presentations. Such tissue-specific clinical symptoms suggest the presence of multiple isoforms of the subunits, but subunit isoforms have not been previously reported. In the present study, we identified two distinct cDNAs for the human flavoprotein subunit (Fp) from a single individual, and demonstrated expression of these two isoforms in skeletal muscle, liver, brain, heart and kidney. Interestingly, one of the Fp isoforms was encoded as an intronless gene. 相似文献
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M. Colin M. -P. Dorthu F. Duby C. Remacle M. Dinant M. -R. Wolwertz C. Duyckaerts F. Sluse R. F. Matagne 《Molecular genetics and genomics : MGG》1995,249(2):179-184
Mitochondrial mutants of the green alga Chlamydomonas reinhardtii that are inactivated in the cytochrome pathway of respiration have previously been isolated. Despite the fact that the alternative oxidase pathway is still active the mutants have lost the capacity to grow heterotrophically (dark + acetate) and display reduced growth under mixotrophic conditions (light + acetate). In crosses between wild-type and mutant cells, the meiotic progeny only inherit the character transmitted by the mt ? parent, which indicates that the mutations are located in the 15.8 kb linear mitochondrial genome. Two new mutants (dum-18 and dum-19) have now been isolated and characterized genetically, biochemically and at the molecular level. In addition, two previously isolated mutants (dum-11 and dum-15) were characterized in more detail. dum-11 contains two types of deleted mitochondrial DNA molecules: 15.1 kb monomers lacking the subterminal part of the genome, downstream of codon 147 of the apocytochrome b (COB) gene, and dimers resulting from head-to-head fusion of asymmetrically deleted monomers (15.1 and 9.5 kb DNA molecules, respectively). As in the wild type, the three other mutants contain only 15.8 kb mitochondrial DNA molecules. dum-15 is mutated at codon 140 of the COB gene, a serine (TCT) being changed into a tyrosine (TAC). dum-18 and dum-19 both inactivate cytochrome c oxidase, as a result of frameshift mutations (addition or deletion of 1 bp) at codons 145 and 152, respectively, of the COX1 gene encoding subunit I of cytochrome c oxidase. In a total of ten respiratory deficient mitochondrial mutants characterized thus far, only mutations located in COB or COXI have been isolated. The possibility that the inactivation of the other mitochondrial genes is lethal for the cells is discussed. 相似文献
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Human complex II (succinate-ubiquinone oxidoreductase): cDNA cloning of iron sulfur (Ip) subunit of liver mitochondria 总被引:3,自引:0,他引:3
K Kita H Oya R B Gennis B A Ackrell M Kasahara 《Biochemical and biophysical research communications》1990,166(1):101-108
Complex II (succinate-ubiquinone oxidoreductase) is an important enzyme complex of both the tricarboxylic acid cycle and of the aerobic respiratory chains of mitochondria in eukaryotic cell and prokaryotic organisms. In this study, the amino acid sequence of iron sulfur-subunit in human liver mitochondria was deduced from cDNA which was isolated by immunoscreening a human liver lambda gtll cDNA library. An isolated clone contains an open reading frame of 786 nucleotides and encodes a mature protein of 252 amino acids with a molecular weight of 28,804. The amino acid sequence was highly homologous with that of bovine heart (94.1%) which has been determined from the purified peptide and that of Escherichia coli sdh B product (50.8%). Striking sequence conservation was found around the three cysteine-rich clusters which have been thought to comprise the iron-sulfur centers of the enzyme. This is the first report on the cDNA sequence of mitochondrial complex II. 相似文献
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Queuosine (Q) is a 7-deazaguanosine found in the first position of the anticodon of tRNAs that recognize NAU and NAC codons (Tyr, Asn, Asp and His). Eukaryotes synthesize Q by the base-for-base exchange of queuine (Q base) for guanine in the unmodified tRNA, a reaction catalyzed by TGT. A search of the human EST database for sequences with significant homology to the well studied TGT from Escherichia coli identified several candidates for full-length (1.3-1.4 kb) cDNA clones. Three candidate cDNA clones, available from IMAGE Consortium, LLNL, (Lennon et al., 1996, Genomics 33, 151-152) were obtained: IMAGE Clone Id Nos. 611146, 1422928, and 72154. Here we report the complete sequences of these clones. IMAGE:72154 contains an ORF encoding a 44 kDa polypeptide with high homology to bacterial TGTs and was subcloned into the mammalian expression vector pMAMneo-Cat. When this construct was transfected into the TGT-negative cell line, GC(3)/c1 (Gündüz et al., 1992, Biochim. Biophys. Acta 1139, 229-238), it restored the ability of the cells to form Q-containing tRNA. This TGT cDNA sequence is encoded in human chromosome 19 clone CTC-539A10 (GenBank accession no. AC011475), enabling determination of the exon-intron boundaries for the TGT gene. The sequence of IMAGE:611146 is 5'-truncated by 76 bp compared to that from IMAGE:72154 and, except for two differences in the 3'-non-coding region, the remainder of the sequence is identical to that of IMAGE:72154. IMAGE:1422928 is a 1390 bp chimera: the 5'-portion, bp 1-708, is identical to a genomic DNA sequence from chromosome 15 (GenBank accession no. AC067805, bp 148976-149683); the 3'-end, bp 726-1390, is identical to the 3'-end of the TGT cDNA sequence from IMAGE:611146. 相似文献
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Bovine heart ubiquinol: cytochrome c oxidoreductase in Triton X-100 is split with guanidine into a number of fractions. A new method for measuring antimycin binding is developed using extraction with pentanol of the reversibly bound antimycin. By this method and the normal titration method, antimycin-binding capacity is found in a fraction containing a small subunit with a molecular mass of about 12000. This polypeptide was associated with cytochrome c1 but is probably not the 'hinge protein'. Fractions that contain cytochrome b did not show binding by the pentanol-extraction method. 相似文献
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Yeast ubiquinol: cytochrome c oxidoreductase is still active after inactivation of the gene encoding the 17-kDa subunit VI 总被引:2,自引:0,他引:2
P J Schoppink W Hemrika J M Reynen L A Grivell J A Berden 《European journal of biochemistry》1988,173(1):115-122
The single nuclear gene encoding the 17-kDa subunit VI of yeast ubiquinol: cytochrome c oxidoreductase has been inactivated by one-step gene disruption. Disruption was verified by Southern blot analysis of nuclear DNA and immunoblotting. Cells lacking the 17-kDa protein are still capable of growth on glycerol and they contain all other subunits of complex III at wild-type levels, implying that the 17-kDa subunit is not essential for either assembly of complex III, or its function. In vitro, electron transport activity of complex III of mutant cells is about 40% of the wild-type complex, but for the total respiratory chain no significant differences in activity was measured between mutant and wild type. The energy-transducing capacity of the complex is not reduced in the absence of the 17-kDa protein. In a relatively high proportion of the transformants, disruption of the 17-kDa gene was accompanied by the appearance of a second mutation causing a petite phenotype. In these cells which lack cytochrome b, the presence of the 17-kDa protein (after complementation) results in stabilization of cytochrome c1. 相似文献
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Purification and some properties of the small subunit of cytochrome b558 from human neutrophils 总被引:2,自引:0,他引:2
T Yamaguchi T Hayakawa M Kaneda K Kakinuma A Yoshikawa 《The Journal of biological chemistry》1989,264(1):112-118
We have attempted to purify the heme moiety of cytochrome b558 from human neutrophils. Cytochrome b558 was solubilized from the crude membrane fraction which was pretreated with both 1 M potassium phosphate buffer and 1% octyl glucoside at low ionic strength. The solubilization of cytochrome b558 was carried out efficiently with 1.6% octyl glucoside in the presence of 100 mM phosphate buffer. Solubilized cytochrome b558 was purified by hydroxylapatite, DEAE-Sephacel, and Mono Q fast protein liquid chromatography. The specific content of purified cytochrome b558 was 37 nmol/mg of protein. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of purified cytochrome b558 revealed a single band of 20,000 Da. The large subunit of cytochrome b558, which has been reported by others, could not be found in purified cytochrome b558 even with silver staining. The amino acid composition of the heme-containing moiety of cytochrome b558 was abundant in hydrophobic amino acids. The circular dichroism spectra of both oxidized and reduced b558-type cytochromes exhibited bilobed bands with wavelengths of crossover points closely corresponding to those of the maxima in the optical absorbance spectra at the Soret region. Furthermore, there were some differences in the shoulders and peak widths of CD spectra between oxidized and reduced b558-type cytochromes. These results indicate that this method provides the purification of the small subunit of human cytochrome b558 which is the heme-carrying subunit of cytochrome b558, and suggest that cytochrome b558 has heme-heme interaction and some conformational changes in the alternation of the redox state. 相似文献
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The apoprotein of yeast cytochrome b is translated on mitochondrial ribosomes and coded for by a split gene which is located in the COB-BOX region on mitochondrial DNA. With the aid of an antibody against cytochrome b, we identified the cytochrome b-cross-reacting polypeptides of respiration-deficient mutants mapping either in coding or intervening sequences of the cytochrome b gene. Most mutations in the coding regions caused the accumulation of a single apocytochrome b fragment whose apparent molecular weight (12,000 to 26,600) depended on the map position of the mutation. In contrast, mutations in putative intervening sequences often led to multiple new polypeptides immunologically related to apocytochrome b. Some of these abnormal polypeptides were considerably larger than wild type apocytochrome b. This suggests that mutations in intervening sequences can thus generate aberrant polypeptide products. 相似文献
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The proteasome subunit DELTA is unusually closely related to the major histocompatibility complex (MHC)-linked proteasome subunit, LMP2. The sequence of a mouse cDNA for DELTA confirms that this 22 100 M
r proteasome subunit is highly conserved across species. Sequence analysis of the mouse gene encoding DELTA, designated Lmp19, indicates that it consists of six exons and five introns, similar to the Lmp2 gene. The 5 upstream region lacks a TATA regulatory sequence, which is also absent from proteasome genes isolated from Drosophila. BXD recombinant inbred (RI) mice were used to map the potential chromosomal location of Lmp19, and revealed that the DELTA subunit has related sequences present on two different mouse chromosomes, chromosomes 1 and 11. Typing of 89 progeny from a C57BL/6J X Mus spretus DNA backcross panel (BSS) confirmed the chromosome 1 assignment. Southern hybridization with a polymerase chain reaction-generated Lmp19 intron 2-specific probe indicates that the Lmp19 genomic clone corresponds to the sequence on chromosome 11, and further suggests that the chromosome 1 copy represents a processed pseudogene (Lmp19-ps1). 相似文献
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Mutational analysis of the mouse mitochondrial cytochrome b gene 总被引:13,自引:0,他引:13
The protonmotive cytochrome b protein of the mitochondrial bc1 respiratory chain complex contains two reactions centers, designated Qo and Qi, which can be distinguished by the effects of different inhibitors. The nucleotide sequences have been determined of the mitochondrial cytochrome b genes from a series of mouse cell mutants selected for increased inhibitor resistance. Each mutant contains a single nucleotide change which results in an amino acid substitution. When the proximity of the altered amino acid residues to the histidines involved in heme ligation is considered, the results support a model for cytochrome b folding in which there are eight transmembrane domains rather than the nine of the Widger-Saraste model. Replacement of the Gly38 residue by valine results in resistance to the Qi inhibitors antimycin A and funiculosin but not 2-n-heptyl-hydroxyquinoline-N-oxide. Based upon sequence comparisons of mitochondrial and bacterial cytochrome b and chloroplast b6 proteins, the region of the molecule involved in antimycin binding is as highly conserved as those domains involved in heme ligation. It is suggested that the antimycin binding domain of cytochrome b is involved in forming the Qi reaction center. Alterations of the Gly142 and Thr147 residues result in resistance to myxothiazol and stimatellin, respectively. While both inhibitors block the Qo reaction center, the two mutations do not confer cross-resistance to each other. This region of cytochrome b is the most highly conserved during evolution and these inhibitor binding sites probably occur within the protein domain constituting the Qo reaction center. In addition, there is a less conserved region of the protein, defined by the Leu294 residue, which may function in binding the hydrophobic portions of Qo inhibitors. 相似文献
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Heterochromatic regions of eukaryotic genomes contain multiple functional elements involved in chromosomal dynamics, as well as multiple housekeeping genes. Cytological and molecular peculiarities of heterochromatic loci complicate genetic studies based on standard approaches developed using euchromatic genes. Here, we report the development of an RNAi-based knockdown transgenic construct and red fluorescent reporter transgene for a small gene, Tim17b, which localizes in constitutive heterochromatin of Drosophila melanogaster third chromosome and encodes a mitochondrial translocase subunit. We demonstrate that Tim17b protein is required strictly for protein delivery to mitochondrial matrix. Knockdown of Tim17b completely disrupts functions of the mitochondrial translocase complex. Using fluorescent recovery after photobleaching assay, we show that Tim17b protein has a very stable localization in the membranes of the mitochondrial network and that its exchange rate is close to zero when compared with soluble proteins of mitochondrial matrix. These results confirm that we have developed comprehensive tools to study functions of heterochromatic Tim17b gene. 相似文献
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E Randi N Mucci M Pierpaoli E Douzery 《Proceedings. Biological sciences / The Royal Society》1998,265(1398):793
The entire mitochondrial cytochrome b (cyt b) gene was compared for 11 species of the artiodactyl family Cervidae, representing all living subfamilies, i.e., the antlered Cervinae (Cervus elaphus, C. nippon, Dama dama), Muntiacinae (Muntiacus reevesi), and Odocoileinae (Odocoileus hemionus, Mazama sp., Capreolus capreolus, C. pygargus, Rangifer tarandus, Alces alces); and the antlerless Hydropotinae (Hydropotes inermis). Phylogenetic analyses using Tragulidae, Antilocapridae, Giraffidae and Bovidae as outgroups provide evidence for three multifurcating principal clades within the monophyletic family Cervidae. First, Cervinae and Muntiacus are joined in a moderately-to-strongly supported clade of Eurasian species. Second, Old World Odocoileinae (Capreolus and Hydropotes) associate with the Holarctic Alces. Third, New World Odocoileinae (Mazama and Odocoileus) cluster with the Holarctic Rangifer. The combination of mitochondrial cyt b and nuclear k-casein sequences increases the robustness of these three clades. The Odocoileini + Rangiferini clade is unambiguously supported by a unique derived cranial feature, the expansion of the vomer which divides the choana. Contrasting with current taxonomy, Hydropotes is not the sister group of all the antlered deers, but it is nested within the Odocoileinae. Therefore, Hydropotes lost the antlers secondarily. Thus, the mitochondrial cyt b phylogeny splits Cervidae according to plesiometacarpal (Cervinae + Muntiacinae) versus telemetacarpal (Odocoileinae + Hydropotinae) conditions, and suggests paraphyly of antlered deer. 相似文献