Melo Ana M P, Lobo Susana A L, Sousa Filipa L, Fernandes Andreia S, Pereira Manuela M, Hreggvidsson Gudmundur O, Kristjansson Jacob K, Saraiva Lígia M, Teixeira Miguel
Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, Apartado 127, 2781-901 Oeiras, Portugal.
Biochim Biophys Acta. 2005 Aug 15;1709(1):95-103. doi: 10.1016/j.bbabio.2005.06.003.
The NADH:menaquinone oxidoreductase (Nqo) is one of the enzymes present in the respiratory chain of the thermohalophilic bacterium Rhodothermus marinus. The genes coding for the R. marinus Nqo subunits were isolated and sequenced, clustering in two operons [nqo1 to nqo7 (nqoA) and nqo10 to nqo14 (nqoB)] and two independent genes (nqo8 and nqo9). Unexpectedly, two genes encoding homologues of a NhaD Na+/H+ antiporter (NhaD) and of a pterin-4alpha-carbinolamine dehydratase (PCD) were identified within nqoB, flanked by nqo13 and nqo14. Eight conserved motives to harbour iron-sulphur centres are identified in the deduced primary structures, as well as two consensus sequences to bind nucleotides, in this case NADH and FMN. Moreover, the open-reading-frames of the putative NhaD and PCD were shown to be co-transcribed with the other complex I genes encoded by nqoB. The possible role of these two genes in R. marinus complex I is discussed.
甲萘醌氧化还原酶（Nqo）是嗜热嗜盐细菌海栖热袍菌呼吸链中存在的一种酶。编码海栖热袍菌Nqo亚基的基因被分离并测序，它们聚集在两个操纵子[nqo1至nqo7（nqoA）和nqo10至nqo14（nqoB）]以及两个独立基因（nqo8和nqo9）中。出乎意料的是，在nqoB内鉴定出两个编码NhaD Na⁺/H⁺反向转运蛋白（NhaD）和蝶呤-4α-甲醇胺脱水酶（PCD）同源物的基因，两侧分别是nqo13和nqo14。在推导的一级结构中鉴定出八个保守的铁硫中心结构基序，以及两个结合核苷酸的共有序列，在这种情况下是NADH和FMN。此外，推定的NhaD和PCD的开放阅读框显示与nqoB编码的其他复合体I基因共转录。讨论了这两个基因在海栖热袍菌复合体I中的可能作用。
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