Oxygen detoxification in the strict anaerobic archaeon Archaeoglobus fulgidus: superoxide scavenging by neelaredoxin. 2000

I A Abreu, and L M Saraiva, and J Carita, and H Huber, and K O Stetter, and D Cabelli, and M Teixeira
Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal.

Archaeoglobus fulgidus is a hyperthermophilic sulphate-reducing archaeon. It has an optimum growth temperature of 83 degrees C and is described as a strict anaerobe. Its genome lacks any homologue of canonical superoxide (O2.-) dismutases. In this work, we show that neelaredoxin (Nlr) is the main O2.- scavenger in A. fulgidus, by studying both the wild-type and recombinant proteins. Nlr is a 125-amino-acid blue-coloured protein containing a single iron atom/molecule, which in the oxidized state is high spin ferric. This iron centre has a reduction potential of +230 mV at pH 7.0. Nitroblue tetrazolium-stained gel assays of cell-soluble extracts show that Nlr is the main protein from A. fulgidus which is reactive towards O2.-. Furthermore, it is shown that Nlr is able to both reduce and dismutate O2.-, thus having a bifunctional reactivity towards O2.-. Kinetic and spectroscopic studies indicate that Nlr's superoxide reductase activity may allow the cell to eliminate O2.- quickly in a NAD(P)H-dependent pathway. On the other hand, Nlr's superoxide dismutation activity will allow the cell to detoxify O2.- independently of the cell redox status. Its superoxide dismutase activity was estimated to be 59 U mg-1 by the xanthine/xanthine oxidase assay at 25 degrees C. Pulse radiolysis studies with the isolated and reduced Nlr proved unambiguously that it has superoxide dismutase activity; at pH 7.1 and 83 degrees C, the rate constant is 5 x 106 M-1 s-1. Besides the superoxide dismutase activity, soluble cell extracts of A. fulgidus also exhibit catalase and NAD(P)H/oxygen oxidoreductase activities. By putting these findings together with the entire genomic data available, a possible oxygen detoxification mechanism in A. fulgidus is discussed.

UI MeSH Term Description Entries
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D010088 Oxidoreductases The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9) Dehydrogenases,Oxidases,Oxidoreductase,Reductases,Dehydrogenase,Oxidase,Reductase
D010100 Oxygen An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration. Dioxygen,Oxygen-16,Oxygen 16
D002352 Carrier Proteins Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes. Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D004579 Electron Transport The process by which ELECTRONS are transported from a reduced substrate to molecular OXYGEN. (From Bennington, Saunders Dictionary and Encyclopedia of Laboratory Medicine and Technology, 1984, p270) Respiratory Chain,Chain, Respiratory,Chains, Respiratory,Respiratory Chains,Transport, Electron
D000595 Amino Acid Sequence The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION. Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D000693 Anaerobiosis The complete absence, or (loosely) the paucity, of gaseous or dissolved elemental oxygen in a given place or environment. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed) Anaerobic Metabolism,Anaerobic Metabolisms,Anaerobioses,Metabolism, Anaerobic,Metabolisms, Anaerobic
D001426 Bacterial Proteins Proteins found in any species of bacterium. Bacterial Gene Products,Bacterial Gene Proteins,Gene Products, Bacterial,Bacterial Gene Product,Bacterial Gene Protein,Bacterial Protein,Gene Product, Bacterial,Gene Protein, Bacterial,Gene Proteins, Bacterial,Protein, Bacterial,Proteins, Bacterial
D013481 Superoxides Highly reactive compounds produced when oxygen is reduced by a single electron. In biological systems, they may be generated during the normal catalytic function of a number of enzymes and during the oxidation of hemoglobin to METHEMOGLOBIN. In living organisms, SUPEROXIDE DISMUTASE protects the cell from the deleterious effects of superoxides. Superoxide Radical,Superoxide,Superoxide Anion
D013482 Superoxide Dismutase An oxidoreductase that catalyzes the reaction between SUPEROXIDES and hydrogen to yield molecular oxygen and hydrogen peroxide. The enzyme protects the cell against dangerous levels of superoxide. Hemocuprein,Ag-Zn Superoxide Dismutase,Cobalt Superoxide Dismutase,Cu-Superoxide Dismutase,Erythrocuprein,Fe-Superoxide Dismutase,Fe-Zn Superoxide Dismutase,Iron Superoxide Dismutase,Manganese Superoxide Dismutase,Mn-SOD,Mn-Superoxide Dismutase,Ag Zn Superoxide Dismutase,Cu Superoxide Dismutase,Dismutase, Ag-Zn Superoxide,Dismutase, Cobalt Superoxide,Dismutase, Cu-Superoxide,Dismutase, Fe-Superoxide,Dismutase, Fe-Zn Superoxide,Dismutase, Iron Superoxide,Dismutase, Manganese Superoxide,Dismutase, Mn-Superoxide,Dismutase, Superoxide,Fe Superoxide Dismutase,Fe Zn Superoxide Dismutase,Mn SOD,Mn Superoxide Dismutase,Superoxide Dismutase, Ag-Zn,Superoxide Dismutase, Cobalt,Superoxide Dismutase, Fe-Zn,Superoxide Dismutase, Iron,Superoxide Dismutase, Manganese

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