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  • 1
    Electronic Resource
    Electronic Resource
    A cytochrome aa3-type quinol oxidase from Desulfurolobus ambivalens, the most acidophilic archaeon (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 117 (1994), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Membranes of the extremely thermoacidophilic archaeon Desulfurolobus ambivalens grown under aerobic conditions contain a quinol oxidase of the cytochrome aa3-type as the most prominent hemoprotein. The partially purified enzyme consists of three polypeptide subunits with apparent molecular masses of 40, 27 and 20 kDa and contains two heme A molecules and one copper atom. CO difference spectra suggest one heme to be a heme a3-centre. The EPR spectra indicate the presence of a low-spin and a high-spin heme species. Redox titrations of the solubilized enzyme show the presence of two reduction processes, with apparent potentials of + 235 and + 330 mV. The enzyme cannot oxidize reduced cytochrome c, but rather serves as an oxidase of caldariella quinone. Due to their very simple composition, D. ambivalens cell appear as a promising candidate to study Structure-function relationships of cytochrome aa3 in the integral membrane state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1994.tb06779.x
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  • 2
    Electronic Resource
    Electronic Resource
    Studies of the Electron Transport Chain of the Euryarcheon Halobacterium salinarum: Indications for a Type II NADH Dehydrogenase and a Complex III Analog (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 443-453 
    Details
    ISSN: 1573-6881
    Keywords: Archea ; inhibitors ; NADH dehydrogenase ; complex III ; cytochromes ; Rieske iron–sulfur cluster ; terminal oxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The components involved in the respiratory system of the euryarcheon Halobacterium salinarum were investigated by spectroscopic and polarographic techniques. Previous results about the cytochrome composition could be verified. However, under low oxygen tension, the expression of a d-type cytochrome was detected. Membranes exerted an NADH– and succinate–cytochrome-c oxidoreductase as well as an NADH and succinate oxidase activity. These activities could be blocked by the following inhibitors: 7-jodocarboxylic acid, giving evidence for the presence of a type II NADH dehydrogenase, antimycin A, and myxothiazol, indicating the presence of a complex III analog, and the typical succinate dehydrogenase (SDH) and terminal oxidase inhibitors. Complex I inhibitors like rotenone and annonine were inactive, clearly excluding the presence of a coupled NADH dehydrogenase. In addition, no [Fe-S] resonances in the region of the NADH dehydrogenase (NDH) clusters could be observed after NADH addition. One of the terminal oxidases could be shown to act as a cytochrome-c oxidase with a K m value of 37 μM and an activation energy of 23.7 kJ/mol. The relative molecular mass of the endogenous c-type cytochrome could be determined as 14.1 kD. The complex III analog could be enriched after detergent extraction with Triton X-100 and hydroxylapatite (HTP) chromatography. The partially purified complex contained a Rieske iron–sulfur cluster, b- and c-type cytochromes, and was catalytically active in the decylubiquinone–cytochrome-c oxidoreductase assay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020538129400
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  • 3
    Electronic Resource
    Electronic Resource
    A Novel Rieske Iron-Sulfur Protein from the Hyperthermophilic Crenarchaeon Pyrobaculum aerophilum: Sequencing of the Gene, Expression in E. coli and Characterization of the Protein (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 119-128 
    Details
    ISSN: 1573-6881
    Keywords: pyrobaculum aerophilum ; archaea ; hyperthermophile ; rieske protein ; sequence ; expression ; redox potential ; pH-dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The crenarchaeon Pyrobaculum aerophilum is with an optimalgrowth temperature of 100 °C one of the most thermophilic organisms knownto possess an aerobic respiratory chain. The analysis of DNA sequences fromthe Pyrobaculum genome project lead to the identification of an openreading frame potentially coding for a Rieske iron-sulfur protein. Thecomplete gene (named parR) was cloned and sequenced. The deducedamino acid sequence displays unusual amino acid exchanges and a so farunknown sequence insertion. The N-terminus shows similarities to bacterialsignal sequences. Several forms of the gene were expressed in E.coli in order to verify the classification as a Rieske protein and tofacilitate biophysical studies. Soluble, thermo-stable proteins withcorrectly inserted iron-sulfur clusters were expressed from two versions ofthe gene. The Δ1–23 truncated holo-protein is redox active. Itdisplays the typical spectroscopic properties of a Rieske protein. The redoxpotential was determined to be +215 mV at pH 6.5 and is pH dependentabove pH 7.5 revealing the influence of two protonation equilibria with pKavalues of 8.1 and 9.8. Phylogenetic analysis demonstrates that the parRprotein clusters together with the two other available archaeal Rieskesequences from Sulfolobus on a separate branch of the phylogenetictree apart from the proteins from thermophilic bacteria like Aquifexand Thermus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005447710894
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