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  • 1
    Online Resource
    Online Resource
    Giardia intestinalis Incorporates Heme into Cytosolic Cytochrome b 5
    American Society for Microbiology ; 2014
    In:  Eukaryotic Cell Vol. 13, No. 2 ( 2014-02), p. 231-239
    Details
    In: Eukaryotic Cell, American Society for Microbiology, Vol. 13, No. 2 ( 2014-02), p. 231-239
    Abstract: The anaerobic intestinal pathogen Giardia intestinalis does not possess enzymes for heme synthesis, and it also lacks the typical set of hemoproteins that are involved in mitochondrial respiration and cellular oxygen stress management. Nevertheless, G. intestinalis may require heme for the function of particular hemoproteins, such as cytochrome b 5 (cyt b 5 ). We have analyzed the sequences of eukaryotic cyt b 5 proteins and identified three distinct cyt b 5 groups: group I, which consists of C-tail membrane-anchored cyt b 5 proteins; group II, which includes soluble cyt b 5 proteins; and group III, which comprises the fungal cyt b 5 proteins. The majority of eukaryotes possess both group I and II cyt b 5 proteins, whereas three Giardia paralogs belong to group II. We have identified a fourth Giardia cyt b 5 paralog (gCYTb5-IV) that is rather divergent and possesses an unusual 134-residue N-terminal extension. Recombinant Giardia cyt b 5 proteins, including gCYTb5-IV, were expressed in Escherichia coli and exhibited characteristic UV-visible spectra that corresponded to heme-loaded cyt b 5 proteins. The expression of the recombinant gCYTb5-IV in G. intestinalis resulted in the increased import of extracellular heme and its incorporation into the protein, whereas this effect was not observed when gCYTb5-IV containing a mutated heme-binding site was expressed. The electrons for Giardia cyt b 5 proteins may be provided by the NADPH-dependent Tah18-like oxidoreductase GiOR-1. Therefore, GiOR-1 and cyt b 5 may constitute a novel redox system in G. intestinalis . To our knowledge, G. intestinalis is the first anaerobic eukaryote in which the presence of heme has been directly demonstrated.
    Type of Medium: Online Resource
    ISSN: 1535-9778 , 1535-9786
    URL: Article
    DOI: 10.1128/EC.00200-13
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2014
    detail.hit.zdb_id: 2071564-X
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Secondary alcohol dehydrogenase catalyzes the reduction of exogenous acetone to 2‐propanol in Trichomonas vaginalis
    Wiley ; 2012
    In:  The FEBS Journal Vol. 279, No. 15 ( 2012-08), p. 2768-2780
    Details
    In: The FEBS Journal, Wiley, Vol. 279, No. 15 ( 2012-08), p. 2768-2780
    Abstract: Secondary alcohols such as 2‐propanol are readily produced by various anaerobic bacteria that possess secondary alcohol dehydrogenase (S‐ADH), although production of 2‐propanol is rare in eukaryotes. Specific bacterial‐type S‐ADH has been identified in a few unicellular eukaryotes, but its function is not known and the production of secondary alcohols has not been studied. We purified and characterized S‐ADH from the human pathogen Trichomonas vaginalis . The kinetic properties and thermostability of T. vaginalis S‐ADH were comparable with bacterial orthologues. The substantial activity of S‐ADH in the parasite’s cytosol was surprising, because only low amounts of ethanol and trace amounts of secondary alcohols were detected as metabolic end products. However, S‐ADH provided the parasite with a high capacity to scavenge and reduce external acetone to 2‐propanol. To maintain redox balance, the demand for reducing power to metabolize external acetone was compensated for by decreased cytosolic reduction of pyruvate to lactate and by hydrogenosomal metabolism of pyruvate. We speculate that hydrogen might be utilized to maintain cytosolic reducing power. The high activity of Tv ‐S‐ADH together with the ability of T. vaginalis to modulate the metabolic fluxes indicate efficacious metabolic responsiveness that could be advantageous for rapid adaptation of the parasite to changes in the host environment.
    Type of Medium: Online Resource
    ISSN: 1742-464X , 1742-4658
    URL: Issue
    URL: Article
    DOI: 10.1111/ejb.2012.279.issue-15
    DOI: 10.1111/j.1742-4658.2012.08661.x
    Language: English
    Publisher: Wiley
    Publication Date: 2012
    detail.hit.zdb_id: 2172518-4
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    NIF-type iron-sulfur cluster assembly system is duplicated and distributed in the mitochondria and cytosol of Mastigamoeba balamuthi
    Proceedings of the National Academy of Sciences ; 2013
    In:  Proceedings of the National Academy of Sciences Vol. 110, No. 18 ( 2013-04-30), p. 7371-7376
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 110, No. 18 ( 2013-04-30), p. 7371-7376
    Abstract: In most eukaryotes, the mitochondrion is the main organelle for the formation of iron-sulfur (FeS) clusters. This function is mediated through the iron-sulfur cluster assembly machinery, which was inherited from the α-proteobacterial ancestor of mitochondria. In Archamoebae, including pathogenic Entamoeba histolytica and free-living Mastigamoeba balamuthi , the complex iron-sulfur cluster machinery has been replaced by an ε-proteobacterial nitrogen fixation (NIF) system consisting of two components: NifS (cysteine desulfurase) and NifU (scaffold protein). However, the cellular localization of the NIF system and the involvement of mitochondria in archamoebal FeS assembly are controversial. Here, we show that the genes for both NIF components are duplicated within the M. balamuthi genome. One paralog of each protein contains an amino-terminal extension that targets proteins to mitochondria (NifS-M and NifU-M), and the second paralog lacks a targeting signal, thereby reflecting the cytosolic form of the NIF machinery (NifS-C and NifU-C). The dual localization of the NIF system corresponds to the presence of FeS proteins in both cellular compartments, including detectable hydrogenase activity in Mastigamoeba cytosol and mitochondria. In contrast, E. histolytica possesses only single genes encoding NifS and NifU, respectively, and there is no evidence for the presence of the NIF machinery in its reduced mitochondria. Thus, M. balamuthi is unique among eukaryotes in that its FeS cluster formation is mediated through two most likely independent NIF machineries present in two cellular compartments.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1219590110
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2013
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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