Iismaa S E, Watson J M
CSIRO Division of Plant Industry, Canberra City, Australia.
Mol Microbiol. 1989 Jul;3(7):943-55. doi: 10.1111/j.1365-2958.1989.tb00244.x.
The nifA gene has been identified between the fixX and nifB genes in the clover microsymbiont Rhizobium leguminosarum biovar trifolii (R.I. bv. trifolii) strain ANU843. Expression of the nifA gene is induced in the symbiotic state and site-directed mutagenesis experiments indicate that nifA expression is essential for symbiotic nitrogen fixation. Interestingly, the predicted R.I. bv. trifolii NifA protein lacks an N-terminal domain that is present in the homologous proteins from R.I. bv. viciae, Rhizobium meliloti, Bradyrhizobium japonicum, Klebsiella pneumoniae and all other documented NifA proteins. This indicates that this N-terminal domain is not essential for NifA function in R.I. bv. trifolii.
在三叶草根瘤菌（豆科根瘤菌生物变种三叶草（R.I. bv. trifolii））菌株ANU843中，已在fixX和nifB基因之间鉴定出nifA基因。nifA基因的表达在共生状态下被诱导，定点诱变实验表明nifA基因的表达对于共生固氮至关重要。有趣的是，预测的R.I. bv. trifolii NifA蛋白缺乏一个N端结构域，而该结构域存在于R.I. bv. viciae、苜蓿根瘤菌、日本慢生根瘤菌、肺炎克雷伯菌以及所有其他已记录的NifA蛋白的同源蛋白中。这表明该N端结构域对于R.I. bv. trifolii中NifA的功能并非必不可少。
