Oxygen detoxification in the strict anaerobic archaeon Archaeoglobus fulgidus:: superoxide scavenging by Neelaredoxin
Oxygen detoxification in the strict anaerobic archaeon Archaeoglobus fulgidus:: superoxide scavenging by Neelaredoxin
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DOI：
10.1046/j.1365-2958.2000.02121.x
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发表时间：
2000-10-01
影响因子：
3.6
通讯作者：
Teixeira, M
中科院分区：
文献类型：
--
作者：
Abreu, IA;Saraiva, LM;Teixeira, M
荧光古生球菌是一种超嗜热硫酸盐还原古菌。它的最适生长温度为83℃，被描述为严格厌氧菌。其基因组缺乏任何典型超氧化物 (O-2 .(-)) 歧化酶的同源物。在这项工作中，我们通过研究野生型和重组蛋白表明，neelaredoxin (Nlr) 是 A. fulgidus 中主要的 O-2 .(-) 清除剂。 Nlr 是一种由 125 个氨基酸组成的蓝色蛋白质，含有单个铁原子/分子，在氧化状态下是高自旋三价铁。该铁中心在 pH 7.0 时具有 +230 mV 的还原电位。细胞可溶性提取物的硝基蓝四唑染色凝胶分析表明，Nlr 是来自 A. fulgidus 的主要蛋白质，它与 O-2 .(-) 发生反应。此外，显示Nlr能够还原和歧化O-2.(-)，因此对O-2.(-)具有双功能反应性。动力学和光谱研究表明，Nlr 的超氧化物还原酶活性可能允许细胞在 NAD(P)H 依赖性途径中快速消除 O-2 .(-)。另一方面，Nlr 的超氧化物歧化活性将使细胞能够独立于细胞氧化还原状态对 O-2 .(-) 进行解毒。 25℃下黄嘌呤/黄嘌呤氧化酶测定估计其超氧化物歧化酶活性为59 U mg(-1)。对分离和还原的 Nlr 进行的脉冲放射分解研究明确证明它具有超氧化物歧化酶活性；在 pH 7.1 和 83 摄氏度下，速率常数为 5 x 10(6) M-1 s(-1)。除了超氧化物歧化酶活性外，A. fulgidus 的可溶性细胞提取物还表现出过氧化氢酶和 NAD(P)H/氧氧化还原酶活性。通过将这些发现与可用的整个基因组数据结合起来，讨论了 A. fulgidus 中可能的氧解毒机制。
Archaeoglobus fulgidus is a hyperthermophilic sulphate-reducing archaeon. It has an optimum growth temperature of 83 degreesC and is described as a strict anaerobe. Its genome lacks any homologue of canonical superoxide (O-2 .(-)) dismutases. In this work, we show that neelaredoxin (Nlr) is the main O-2 .(-) 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 O-2 .(-). Furthermore, it is shown that Nlr is able to both reduce and dismutate O-2 .(-), thus having a bifunctional reactivity towards O-2 .(-). Kinetic and spectroscopic studies indicate that Nlr's superoxide reductase activity may allow the cell to eliminate O-2 .(-) quickly in a NAD(P)H-dependent pathway. On the other hand, Nlr's superoxide dismutation activity will allow the cell to detoxify O-2 .(-) 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 degreesC. Pulse radiolysis studies with the isolated and reduced Nlr proved unambiguously that it has superoxide dismutase activity; at pH 7.1 and 83 degreesC, the rate constant is 5 x 10(6) 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.