Surpin M A, Moshiri F, Murphy A M, Maier R J
Department of Biology, Johns Hopkins University, Baltimore, MD 21218.
Gene. 1994 May 27;143(1):73-7. doi: 10.1016/0378-1119(94)90607-6.
Bradyrhizobium japonicum, a symbiotic nitrogen-fixing bacterium, has a complex respiratory electron-transport chain, capable of functioning throughout a wide range of oxygen tensions. It does so by synthesizing a number of terminal oxidases, each appropriate for different environmental conditions. Several genes encoding terminal oxidases from B. japonicum have been cloned, but it is unknown what roles these individual oxidases play. In this paper, we describe the cloning and sequencing of the coxX gene encoding the large catalytic subunit for a fourth terminal oxidase from B. japonicum. The coxX gene encodes a 666-amino-acid (aa) protein (M(r) 74,527) that exhibits a high degree of homology to terminal oxidase proteins from a number of prokaryotic and eukaryotic species. This new oxidase exhibits greater homology to the Escherichia coli cytochrome o subunit I than any of the previously reported B. japonicum terminal oxidase genes.
慢生根瘤菌是一种共生固氮细菌，具有复杂的呼吸电子传递链，能够在很宽的氧张力范围内发挥作用。它通过合成多种末端氧化酶来实现这一点，每种氧化酶都适用于不同的环境条件。已经克隆了几个编码慢生根瘤菌末端氧化酶的基因，但这些单个氧化酶发挥什么作用尚不清楚。在本文中，我们描述了慢生根瘤菌第四种末端氧化酶的大催化亚基编码基因coxX的克隆和测序。coxX基因编码一种666个氨基酸（aa）的蛋白质（分子量74,527），它与许多原核和真核物种的末端氧化酶蛋白具有高度同源性。这种新的氧化酶与大肠杆菌细胞色素o亚基I的同源性比以前报道的任何慢生根瘤菌末端氧化酶基因都更高。
