NITRATE REDUCTASE OF ESCHERICHIA-COLI - COMPLETION OF THE NUCLEOTIDE-SEQUENCE OF THE NAR OPERON AND REASSESSMENT OF THE ROLE OF THE ALPHA-SUBUNIT AND BETA-SUBUNIT IN IRON-BINDING AND ELECTRON-TRANSFER
NITRATE REDUCTASE OF ESCHERICHIA-COLI - COMPLETION OF THE NUCLEOTIDE-SEQUENCE OF THE NAR OPERON AND REASSESSMENT OF THE ROLE OF THE ALPHA-SUBUNIT AND BETA-SUBUNIT IN IRON-BINDING AND ELECTRON-TRANSFER
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DOI：
10.1007/bf00331275
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发表时间：
1989-08-01
期刊：
影响因子：
--
通讯作者：
BONNEFOY, V
中科院分区：
文献类型：
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作者：
BLASCO, F;IOBBI, C;BONNEFOY, V
编码大肠杆菌硝酸还原酶的narGHJI操纵子的核苷酸序列已完成。它编码四种多肽NarG、NarH、NarJ和NarI，分子量分别为138.7、57.7、26.5和25.5 kDa。对推导的氨基酸序列的分析未能揭示NarG多肽内任何能够结合铁的结构。相反，在 NarH 多肽中发现了铁硫中心典型的半胱氨酸排列。这表明后者是硝酸还原酶复合物的电子转移单元。这种观点与目前对硝酸还原酶的描述相反。这些发现使我们能够提出硝酸盐还原过程中发生的电子转移步骤的模型。发现 NarG 多肽与许多大肠杆菌钼蛋白表现出高度的同源性。此外，NarG/NarH 和 DmsA/DmsB（编码二甲亚砜还原酶）对之间存在相同的遗传和功能组织以及高度保守的氨基酸片段。
The nucleotide sequence of the narGHJI operon that encodes the nitrate reductase of Escherichia coli was completed. It encodes four polypeptides NarG, NarH, NarJ and NarI of molecular weight 138.7, 57.7, 26.5 and 25.5 kDa, respectively. The analysis of deduced amino acid sequence failed to reveal any structure capable of binding iron within the NarG polypeptide. In contrast, cysteine arrangements typical of iron-sulfur centers were found in the NarH polypeptide. This suggested that the latter is an electron transfer unit of the nitrate reductase complex. Such a view is opposite to the current description of the nitrate reductase. The findings allowed us to propose a model for the electron transfer steps that occur during nitrate reduction. The NarG polypeptide was found to display a high degree of homology with numerous E. coli molybdoproteins. Moreover, the same genetic and functional organizations as well as the presence of highly conserved stretches of amino acids were noted between both NarG/NarH and DmsA/DmsB (encoding the dimethyl sulfoxide reductase) pairs.