Department of Applied Life Science, Faculty of Biotechnology and Life Science, Sojo University, Ikeda, Kumamoto, Japan.
FEMS Microbiol Lett. 2010 Dec;313(1):61-7. doi: 10.1111/j.1574-6968.2010.02122.x. Epub 2010 Sep 30.
A dimeric cytochrome c with an apparent molecular mass of 25 kDa was isolated from an anammox bacterium, strain KSU-1, in a relatively large quantity. This protein was named the NaxLS complex. The spectrum of the oxidized form exhibited a peculiar Soret peak at 419 nm. The reduction of NaxLS was not complete even with the addition of excess dithionite, but was complete with titanium (III) citrate, indicating that the NaxLS complex has a very low redox potential. The genes encoding the two subunits, naxL and naxS, are adjacent on the genome. The deduced amino-acid sequences of the genes showed high identities with those of two genes encoding 'unknown proteins' in the genome of Candidatus Kuenenia stuttgartiensis, but had lower identities with other c-type heme proteins. The electron paramagnetic resonance spectra of NaxLS exhibited low-spin signals of two heme species in the range between g=2.6 and g=1.8, which strongly suggested an unusual His/Cys coordination. This unique coordination might account for the low redox potential of the hemes in NaxLS. NaxLS might participate in the transfer of low redox potential electrons in the intracellular anammoxosome compartment or the cytoplasm.
从一种厌氧氨氧化菌（KSU-1 株）中大量分离出一种二聚细胞色素 c，其表观分子量为 25 kDa。该蛋白被命名为 NaxLS 复合物。氧化形式的光谱在 419nm 处显示出一个特殊的 Soret 峰。即使加入过量的连二亚硫酸盐，NaxLS 的还原也不完全，但与钛 (III) 柠檬酸盐完全还原，表明 NaxLS 复合物具有非常低的氧化还原电位。编码两个亚基 naxL 和 naxS 的基因在基因组上相邻。基因的推导氨基酸序列与 Candidatus Kuenenia stuttgartiensis 基因组中两个编码“未知蛋白”的基因具有高度的同一性，但与其他 c 型血红素蛋白的同一性较低。NaxLS 的电子顺磁共振谱在 g=2.6 和 g=1.8 之间的范围内显示出两种血红素物种的低自旋信号，这强烈表明存在一种不寻常的 His/Cys 配位。这种独特的配位可能是 NaxLS 中血红素低氧化还原电位的原因。NaxLS 可能参与细胞内厌氧氨氧化体隔室或细胞质中低氧化还原电位电子的转移。
