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:1.6.99.5 (NADH dehydrogenase)
2,135 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We report that the mitochondrial genome of Chlamydomonas moewusii has a 22 kb circular map and thus contrasts with the mitochondrial genome of Chlamydomonas reinhardtii, which is linear and about 6 kb shorter. Overlapping restriction fragments spanning over 90% of the C. moewusii mitochondrial DNA (mtDNA) were identified in a clone bank constructed using a Sau3AI partial digest of a C. moewusii DNA fraction enriched for mtDNA by preparative CsCl density gradient centrifugation. Overlapping Sau3AI clones were identified by a chromosome walk initiated with a clone of C. moewusii mtDNA. The mtDNA map was completed by Southern blot analysis of the C. moewusii mtDNA fraction using isolated mtDNA clones. Regions that hybridized to C. reinhardtii or wheat mitochondrial gene probes for subunit I of cytochrome oxidase (cox1), apocytochrome b (cob), three subunits of NADH dehydrogenase (nad1, nad2 and nad5) and the small and the large ribosomal RNAs (rrnS and rrnL, respectively) were localized on the C. moewusii mtDNA map by Southern blot analysis. The results show that the order of genes in the mitochondrial genome of C. moewusii is completely rearranged relative to that of C. reinhardtii.
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PMID:Cloning and characterization of the Chlamydomonas moewusii mitochondrial genome. 175 45

Two long and uninterrupted reading frames, specifying the ND1 and RTL genes, are embedded within fragmented rRNA genes in the 15.8-kb mitochondrial genome of Chlamydomonas reinhardtii, a unicellular green alga. The ND1 gene encodes a subunit of respiratory NADH dehydrogenase, a standard mitochondrial gene, while the RTL gene is related to the reverse transcriptase-like part of some optional introns and plasmids in fungal mitochondria. The universal genetic code is used in both the ND1 and RTL genes; however, the latter is distinguished from the other protein coding genes of C. reinhardtii mtDNA by several characteristics which suggest that RTL may be a more recently acquired gene. Flanking each of the protein coding genes, whose mRNAs are of similar abundance, are some of the 'scrambled' rRNA gene pieces that are a unique feature of C. reinhardtii mtDNA. These sub-genic modules give rise to high-abundance, small-sized pieces of rRNA, which are not spliced in this genetic system. Judging by the observed juxtaposition of transcripts as they hybridize to the genome, the mature rRNA and mRNA species from this region appear to be generated by precise endonucleolytic cleavages of a long RNA precursor. We suggest a model, involving reverse transcription of rRNAs and insertion of the resulting cDNAs into the mitochondrial genome, that might account for the pattern of dispersed rRNA gene pieces in C. reinhardtii mitochondrial DNA.
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PMID:Genes encoding a subunit of respiratory NADH dehydrogenase (ND1) and a reverse transcriptase-like protein (RTL) are linked to ribosomal RNA gene pieces in Chlamydomonas reinhardtii mitochondrial DNA. 246 63

Chlamydomonas reinhardtii mitochondrial (mt)DNA was digested with ClaI + HpaI and shotgun cloned into the M13mp19 vector cleaved with AccI + SmaI. One of the recombinant clones, with a 1.8-kb DNA insert, was completely sequenced using the dideoxy chain-termination method. Besides containing part of the cytochrome b (COB)-encoding gene (cob), this DNA fragment encodes subunit 4 of NADH dehydrogenase (NAD4). The deduced amino acid sequence and hydrophilicity plot indicate that NAD4 is highly hydrophobic. The nad4 gene shows a unique preference for certain codons which are also found in other C. reinhardtii mt proteins. Both the genes encoding NAD4 and COB are shown to be transcriptionally active by Northern hybridization. These closely linked genes suggest that RNA-processing events found in vertebrate mt are present in Chlamydomonas mt as well.
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PMID:Nucleotide sequence of cloned nad4 (urf4) gene from Chlamydomonas reinhardtii mitochondrial DNA. 262 73

The ND4 gene encoding a subunit of respiratory NADH dehydrogenase has been identified on the linear 15.8 kb mitochondrial DNA of Chlamydomonas reinhardtii. The gene maps downstream of ND5. The 1,332 bp nucleotide sequence presented is the first complete reported ND4 sequence from a photoautotrophic organism. The deduced protein of 443 amino acid residues shows 34%, 29% and 27% homology to the protein sequences of Aspergillus amstelodami, Drosophila yakuba and mouse, respectively. ND4 is the fifth and last mitochondrial gene of the NADH dehydrogenase complex on the 15.8 kb mitochondrial genome of C. reinhardtii.
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PMID:Mitochondrial DNA of Chlamydomonas reinhardtii: the ND4 gene encoding a subunit of NADH dehydrogenase. 279 Oct 36

The complete nucleotide sequence of the Chlamydomonas eugametos (Chlamydomonadales, Chlorophyceae, sensu Mattox and Stewart) mitochondrial genome has been determined (22,897 bp, 34.6% G + C). The genes identified in this circular-mapping genome include those for apocytochrome b, subunit 1 of the cytochrome oxidase complex, subunits 1, 2, 4, 5, and 6 of the NADH dehydrogenase complex, discontinuous large and small subunit ribosomal rRNAs and three tRNAs whose anticodons CAU, CCA and UUG are specific for methionine, tryptophan and glutamine, respectively. The C. eugametos mitochondrial DNA (mtDNA), therefore, shares almost the same reduced set of coding functions and similar unusual features of rRNA gene organization with the linear 15.8 kb mtDNA of Chlamydomonas reinhardtii, the only other completely sequenced chlamydomonadalean mtDNA. However, sequence analysis of the C. eugametos mtDNA has revealed the following distinguishing features relative to those of C. reinhardtii: (1) the absence of a reverse transcriptase-like gene homologue, (2) the presence of an additional gene for tRNA(met) that may be a pseudogene, (3) a completely different gene order, (4) transcription of all genes from the same mtDNA strand, (5) a lower G + C content, (6) less pronounced bias in codon usage, and (7) nine group I introns, several of which contain open reading frames coding for potential maturases/endonucleases and two have a nucleotide at the 5' or 3' splice site of the deduced precursor RNAs that deviates from highly conserved nucleotides reported in other group I introns. The features of mitochondrial genome organization and gene content shared by C. eugametos and C. reinhardtii contrast with those of other green algal mtDNAs that have been characterized in detail. The deep evolutionary divergence between these two Chlamydomonas taxa within the Chlamydomonadales suggests that their shared features of mitochondrial genome organization evolved prior to the origin of this group.
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PMID:Complete sequence of the mitochondrial DNA of Chlamydomonas eugametos. 948 40

The 22,704-bp circular mitochondrial DNA (mtDNA) of the chlamydomonad alga Chlorogonium elongatum was completely cloned and sequenced. The genome encodes seven proteins of the respiratory electron transport chain, subunit 1 of the cytochrome oxidase complex (cox1), apocytochrome b (cob), five subunits of the NADH dehydrogenase complex (nad1, nad2, nad4, nad5, and nad6), a set of three tRNAs (Q, W, M), and the large (LSU)- and small (SSU)-subunit ribosomal RNAs. Six group-I introns were found, two each in the cox1, cob, and nad5 genes. In each intron an open reading frame (ORF) related to maturases or endonucleases was identified. Both the LSU and the SSU rRNA genes are split into fragments intermingled with each other and with other genes. Although the average A + T content is 62.2%, GC-rich clusters were detected in intergenic regions, in variable domains of the rRNA genes, and in introns and intron-encoded ORFs. A comparison of the genome maps reveals that C. elongatum and Chlamydomonas eugametos mtDNAs are more closely related to one another than either is to Chlamydomonas reinhardtii mtDNA.
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PMID:The mitochondrial genome of Chlorogonium elongatum inferred from the complete sequence. 976 88

We describe here a new type of mitochondrial mutation (dum24; for dark uniparental minus inheritance) of the unicellular photosynthetic alga Chlamydomonas reinhardtii. The mutant fails to grow under heterotrophic conditions and displays reduced growth under both photoautotrophic and mixotrophic conditions. In reciprocal crosses between mutant and wild-type cells, the meiotic progeny only inherit the phenotype of the mating-type minus parent, indicating that the dum24 mutation exclusively affects the mitochondrial genome. Digestion with various restriction enzymes followed by DNA gel blot hybridizations with specific probes demonstrated that dum24 cells contain four types of altered mitochondrial genomes: deleted monomers lacking cob, nd4, and the 3' end of the nd5 gene; deleted monomers deprived of cob, nd4, nd5, and the 5' end of the cox1 coding sequence; and two types of dimers produced by end-to-end fusions between monomers similarly or differently deleted. Due to these mitochondrial DNA alterations, complex I activity, the cytochrome pathway of respiration, and presumably, the three phosphorylation sites associated with these enzyme activities are lacking in the mutant. The low respiratory rate of the dum24 cells results from the activities of rotenone-resistant NADH dehydrogenase, complex II, and alternative oxidase, with none of these enzymes being coupled to ATP production. To our knowledge, this type of mitochondrial mutation has never been described for photosynthetic organisms or more generally for obligate aerobes.
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PMID:Alteration of dark respiration and reduction of phototrophic growth in a mitochondrial DNA deletion mutant of Chlamydomonas lacking cob, nd4, and the 3' end of nd5. 987 36

The mitochondrial rotenone-sensitive NADH:ubiquinone oxidoreductase (complex I) comprises more than 35 subunits, the majority of which are encoded by the nucleus. In Chlamydomonas reinhardtii, only five components (ND1, ND2, ND4, ND5 and ND6) are coded for by the mitochondrial genome. Here, we characterize two mitochondrial mutants (dum5 and dum17) showing strong reduction or inactivation of complex I activity: dum5 is a 1T deletion in the 3' UTR of nd5 whereas dum17 is a 1T deletion in the coding sequence of nd6. The impact of these mutations and of mutations affecting nd1, nd4 and nd4/nd5 genes on the assembly of complex I is investigated. After separation of the respiratory complexes by blue native (BN)-PAGE or sucrose gradient centrifugation, we demonstrate that the absence of intact ND1 or ND6 subunit prevents the assembly of the 850 kDa whole complex, whereas the loss of ND4 or ND4/ND5 leads to the formation of a subcomplex of 650 kDa present in reduced amount. The implications of our findings for the possible role of these ND subunits on the activity of complex I and for the structural organization of the membrane arm of the enzyme are discussed. In mitochondria from all the strains analyzed, we moreover detected a 160-210 kDa fragment comprising the hydrophilic 49 kDa and 76 kDa subunits of the complex I peripheral arm and showing NADH dehydrogenase activity.
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PMID:Impact of mutations affecting ND mitochondria-encoded subunits on the activity and assembly of complex I in Chlamydomonas. Implication for the structural organization of the enzyme. 1207 58

In the absence of PSII, non-photochemical reduction of plastoquinones (PQs) occurs following NADH or NADPH addition in thylakoid membranes of the green alga Chlamydomonas reinhardtii. The nature of the enzyme involved in this reaction has been investigated in vitro by measuring chlorophyll fluorescence increase in anoxia and light-dependent O(2) uptake in the presence of methyl viologen. Based on the insensitivity of these reactions to rotenone, a type-I NADH dehydrogenase (NDH-1) inhibitor, and their sensitivity to flavoenzyme inhibitors and thiol blocking agents, we conclude to the involvement of a type-II NADH dehydrogenase (NDH-2) in PQ reduction. Intact Chlamydomonas cells placed in anoxia have the property to produce H(2) in the light by a Fe-hydrogenase which uses reduced ferredoxin as an electron donor. H(2) production also occurs in the absence of PSII thanks to the existence of a non-photochemical pathway of PQ reduction. From inhibitors effects, we suggest the involvement of a plastidial NDH-2 in PSII-independent H(2) production in Chlamydomonas. These results are discussed in relation to the absence of ndh genes in Chlamydomonas plastid genome and to the existence of 7 ORFs homologous to type-II NDHs in its nuclear genome.
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PMID:Inhibitor studies on non-photochemical plastoquinone reduction and H(2) photoproduction in Chlamydomonas reinhardtii. 1595 Sep 24

Type II NADH dehydrogenases (NDH-2) are monomeric enzymes that catalyse quinone reduction and allow electrons to enter the respiratory chain in different organisms including higher plant mitochondria, bacteria and yeasts. In this study, an Agrobacterium tumefaciens gene encoding a putative alternative NADH dehydrogenase (AtuNDH-2) was isolated and expressed in Escherichia coli as a (His)6-tagged protein. The purified 46 kDa protein contains FAD as a prosthetic group and oxidizes both NADH and NADPH with similar Vmax values, but with a much higher affinity for NADH than for NADPH. AtuNDH-2 complements the growth (on a minimal medium) of an E. coli mutant strain deficient in both NDH-1 and NDH-2, and is shown to supply electrons to the respiratory chain when incubated with bacterial membranes prepared from this mutant. By measuring photosystem II chlorophyll fluorescence on thylakoid membranes prepared from the green alga Chlamydomonas reinhardtii, we show that AtuNDH-2 is able to stimulate NADH-dependent reduction of the plastoquinone pool. We discuss the possibility of using heterologous expression of NDH-2 enzymes to improve nonphotochemical reduction of plastoquinones and H2 production in C. reinhardtii.
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PMID:Agrobacterium tumefaciens type II NADH dehydrogenase. Characterization and interactions with bacterial and thylakoid membranes. 1688 1


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