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Recombinant Cyclophilins Lack Nuclease Activity. Angel Manteca, 2004.Several single-domain prokaryotic and eukaryotic cyclophilinshave been identified as also being unspecific nucleases witha role in DNA degradation during the lytic processes that accompanybacterial cell death and eukaryotic apoptosis . Evidence is providedhere that the supposed nuclease activity of human and bacterialrecombinant cyclophilins is due to contamination of the proteinsby the host Escherichia coli endonuclease and is not an intrinsicproperty of these proteins. Functional Role for a 2-Oxo Acid Dehydrogenase in the Halophilic Archaeon Haloferax volcanii. Christian Wanner, 2002.The archaeon Haloferax volcanii was previously shown to contain and transcribe the genes for a 2-oxo acid dehydrogenase (OADH) complex, but their presence remained a mystery because no enzymatic activity with any of the known OADH substrates could be found, and an inactivation of one of the genes did not lead to any phenotype . Here we report the identification of an additional oadh gene cluster in the genome of H . volcanii . In contrast to previously known oadh loci, it contains three genes, oadh2A1, oadh2A2, and oadh2ld, with coding capacity for the E1  and E1ß subunits and an unattached lipoyl domain, but it is devoid of the genes for a complete E2 and an E3 . The genes were isolated by complementation of a nitrate respiration-deficient mutant of H . volcanii and therefore were shown to be functional in vivo . Phylogenetic analyses revealed that the deduced E1 and E1ß subunits of OADH2 group with bacterial acetoin dehydrogenases but not with the OADH1 subunits, and thus, H . volcanii has obtained the two gene groups independently . Comparison of the wild type and the mutant allowed us to exclude a function of OADH2 in the aerobic or anaerobic degradation of acetoin or glucose . Instead, it could be shown that OADH2 is important during nitrate-respirative growth on Casamino Acids . Many physiological and biochemical experiments failed to indicate that OADH2 uses any of the previously known OADH substrates . Growth potentials of the mutant were markedly different in media with a single carbon source versus media with mixed carbon sources .
Carbon Monoxide Cycling by Desulfovibrio vulgaris Hildenborough. Gerrit Voordouw, 2002.Sulfate-reducing bacteria, like Desulfovibrio vulgaris Hildenborough, use the reduction of sulfate as a sink for electrons liberated in oxidation reactions of organic substrates . The rate of the latter exceeds that of sulfate reduction at the onset of growth, causing a temporary accumulation of hydrogen and other fermentation products (the hydrogen or fermentation burst) . In addition to hydrogen, D . vulgaris was found to produce significant amounts of carbon monoxide during the fermentation burst . With excess sulfate, the hyd mutant (lacking periplasmic Fe-only hydrogenase) and hmc mutant (lacking the membrane-bound, electron-transporting Hmc complex) strains produced increased amounts of hydrogen from lactate and formate compared to wild-type D . vulgaris during the fermentation burst . Both hydrogen and CO were produced from pyruvate, with the hyd mutant producing the largest transient amounts of CO . When grown with lactate and excess sulfate, the hyd mutant also exhibited a temporary pause in sulfate reduction at the start of stationary phase, resulting in production of 600 ppm of headspace hydrogen and 6,000 ppm of CO, which disappeared when sulfate reduction resumed . Cultures with an excess of the organic electron donor showed production of large amounts of hydrogen, but no CO, from lactate . Pyruvate fermentation was diverse, with the hmc mutant producing 75,000 ppm of hydrogen, the hyd mutant producing 4,000 ppm of CO, and the wild-type strain producing no significant amount of either as a fermentation end product . The wild type was most active in transient production of an organic acid intermediate, tentatively identified as fumarate, indicating increased formation of organic fermentation end products in the wild-type strain . These results suggest that alternative routes for pyruvate fermentation resulting in production of hydrogen or CO exist in D . vulgaris . The CO produced can be reoxidized through a CO dehydrogenase, the presence of which is indicated in the genome sequence .
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