Tóth András, Takács Mária, Groma Géza, Rákhely Gábor, Kovács Kornél L
Institute of Biophysics, Biological Research Center, Hungarian Academy of Sciences, Szeged, Hungary.
FEMS Microbiol Lett. 2008 May;282(1):8-14. doi: 10.1111/j.1574-6968.2008.01085.x. Epub 2008 Mar 18.
Thermococcus litoralis, a hyperthermophilic Archaeon, is able to reduce elemental sulfur during fermentative growth. An unusual gene cluster (nsoABCD) was identified in this organism. In silico analysis suggested that three of the genes (nsoABC) probably originated from Eubacteria and one gene (nsoD) from Archaea. The putative NsoA and NsoB are similar to NuoE- and NuoF-type electron transfer proteins, respectively. NsoC has a unique domain structure and contains a GltD domain, characteristic of glutamate synthase small subunits, which seems to be integrated into a NuoG-type sequence. Flavin and NAD(P)H binding sites and conserved cysteines forming iron-sulfur clusters binding motifs were identified in the protein sequences deduced. The purified recombinant NsoC contains one FAD cofactor per protein molecule and catalyzes the reduction of polysulfide with NADPH as an electron donor and it also reduces oxygen. It was concluded that the Nso complex is a new type of NADPH-oxidizing enzyme using sulfur and/or oxygen as an electron acceptor.
嗜热栖热菌是一种嗜热古菌，在发酵生长过程中能够还原元素硫。在这种生物体中鉴定出了一个不寻常的基因簇（nsoABCD）。计算机分析表明，其中三个基因（nsoABC）可能起源于真细菌，一个基因（nsoD）起源于古菌。推测的NsoA和NsoB分别类似于NuoE型和NuoF型电子转移蛋白。NsoC具有独特的结构域结构，包含一个谷氨酸合酶小亚基特有的GltD结构域，该结构域似乎整合到了NuoG型序列中。在推导的蛋白质序列中鉴定出了黄素和NAD（P）H结合位点以及形成铁硫簇结合基序的保守半胱氨酸。纯化的重组NsoC每个蛋白质分子含有一个FAD辅因子，以NADPH作为电子供体催化多硫化物的还原，并且它也能还原氧气。得出的结论是，Nso复合物是一种新型的以硫和/或氧气作为电子受体的NADPH氧化酶。
