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)

The bidirectional, NAD+-dependent hydrogenase from cyanobacteria is encoded by the structural genes hoxFUYH, which have been found to be clustered, though interspersed with different open reading frames (ORFs), in the heterocystous, N2-fixing Anabaena variabilis and in the unicellular Synechocystis PCC 6803. In another unicellular, non N2-fixing cyanobacterium, Anacystis nidulans, hoxF has now been identified as being separated by at least 16 kb from the residual structural genes hoxUYH. An ORF (termed hoxE gene) is located immediately upstream of hoxF in A. nidulans and in Synechocystis. Its deduced amino acid sequence shows similarities to the NuoE subunit of NADH dehydrogenase I of E. coli, to the homologous subunit of respiratory complex I in mitochondria, and also to the first 104 amino acids of HoxF in A. nidulans and Synechocystis. The diversity in the arrangement of hydrogenase genes in cyanobacteria is puzzling. The subunits HoxE, HoxF, and HoxU of the diaphorase part of the bidirectional hydrogenase have been discussed to be shared both by respiratory complex I and bidirectional hydrogenase in cyanobacteria. Different hoxU mutants were obtained by inserting a lacZKmR cassette into the gene both in A. nidulans and Anacystis PCC 7942. Such mutants showed reduced H2-evolution activities catalyzed by the bidirectional hydrogenase, but had nonimpaired respiratory O2-uptake. A common link between respiratory complex I and the diaphorase part of the bidirectional hydrogenase in cyanobacteria may still exist, but this hypothesis could not be verified in the present study by analyzing defined mutants impaired in one of the diaphorase genes.
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PMID:Unusual gene arrangement of the bidirectional hydrogenase and functional analysis of its diaphorase subunit HoxU in respiration of the unicellular cyanobacterium anacystis nidulans 954 59

NAD(P)(+)-reducing hydrogenases have been described to be composed of a diaphorase (HoxFU) and a hydrogenase (HoxYH) moiety. This study presents for the first time experimental evidence that in cyanobacteria, a fifth subunit, HoxE, is part of this bidirectional hydrogenase. HoxE exhibits sequence identities to NuoE of respiratory complex I of Escherichia coli. The subunit composition of the cyanobacterial bidirectional hydrogenase has been investigated. The oxygen labile enzyme complex was purified to close homogeneity under anaerobic conditions from Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 6301. The 647-fold and 1290-fold enriched purified enzyme has a specific activity of 46 micromol H(2) evolved (min mg protein)(-1) and 15 micromol H(2) evolved (min mg protein)(-1), respectively. H(2)-evolution of the purified enzyme of S. sp. PCC 6803 is highest at 60 degrees C and pH 6.3. Immunoblot experiments, using a polyclonal anti-HoxE antibody, demonstrate that HoxE co-purifies with the hydrogenase activity in S. sp. PCC 6301. SDS-PAGE gels of the purified enzymes revealed six proteins, which were partially sequenced and identified, besides one nonhydrogenase component, as HoxF, HoxU, HoxY, HoxH and, remarkably, HoxE. The molecular weight of the native protein (375 kDa) indicates a dimeric assembly of the enzyme complex, Hox(EFUYH)(2).
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PMID:HoxE--a subunit specific for the pentameric bidirectional hydrogenase complex (HoxEFUYH) of cyanobacteria. 1203 72

Bovine-heart NADH:ubiquinone oxidoreductase (EC 1.6.5.3; Complex I) is the first and most complicated enzyme in the mitochondrial respiratory chain. Biochemistry textbooks and virtually all literature on this enzyme state that it contains one FMN and at least four iron-sulfur clusters. We show here that this statement is incorrect as it is based on erroneous protein determinations. Quantitative amino acid analysis of the bovine Complex I, to our knowledge the first reported thus far, shows that the routine protein-determination methods used for the bovine Complex I overestimate its protein content by up to twofold. The FMN content of the preparations was determined to be at least 1.3-1.4 mol FMN/mol Complex I. The spin concentration of the electron paramagnetic resonance (EPR) signal ascribed to iron-sulfur cluster N2 was determined and accounted for 1.3-1.6 clusters per molecule of Complex I. These results experimentally confirm the hypothesis [FEBS Lett. 485 (2000) 1] that the bovine Complex I contains two FMN groups and two clusters N2. Also the protein content of preparations of the soluble NAD(+)-reducing [NiFe]-hydrogenase (EC 1.12.1.2) from Ralstonia eutropha, which shows clear evolutionary relationships with Complex I, scores too high by the colorimetric protein-determination methods. Determination of the FMN content and the spin concentration of the EPR signal of the [2Fe-2S] cluster shows that this hydrogenase also contains two FMN groups. A third enzyme (Ech), the membrane-bound [NiFe]-hydrogenase from Methanosarcina barkeri which shows an even stronger evolutionary relationship with Complex I, behaves rather normal in protein determinations and contains no detectable acid-extractable FMN in purified preparations.
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PMID:Quantitative amino acid analysis of bovine NADH:ubiquinone oxidoreductase (Complex I) and related enzymes. Consequences for the number of prosthetic groups. 1261 47