Robson R L, Woodley P R, Pau R N, Eady R R
AFRC Institute of Plant Science Research, University of Sussex, Brighton, UK.
EMBO J. 1989 Apr;8(4):1217-24. doi: 10.1002/j.1460-2075.1989.tb03495.x.
Structural genes for the VFe-protein (Ac1V) of the vanadium nitrogenase from Azotobacter chroococcum were cloned and sequenced. The VFe-protein contains three subunit types with Mr of 53,793 (alpha), 52,724 (beta) and 13,274 (delta). alpha and beta subunits show 18 and 15% sequence identity respectively, with alpha and beta subunits of the MoFe-protein of A.chroococcum molybdenum nitrogenase. The genes for the three subunits vnfD (alpha), vnfG (delta) and vnfK (beta) are contiguous and form an operon whose transcription is repressed in response to ammonia. The Fe-protein component of the V-nitrogenase (Ac2V) is the product of nifH* that we have previously cloned and sequenced. This gene was located 2.5 kb upstream of vnfD. A deletion in the vnfD, G and K gene cluster prevents V-dependent nitrogen fixation. A strain defective in both V-nitrogenase and Mo-nitrogenase structural genes showed no residual nitrogen fixing capacity arguing against the presence of a third nitrogen fixation system in this organism.
对来自褐球固氮菌的钒固氮酶的VFe蛋白（Ac1V）的结构基因进行了克隆和测序。VFe蛋白包含三种亚基类型，其分子量分别为53,793（α）、52,724（β）和13,274（δ）。α和β亚基分别与褐球固氮菌钼固氮酶的MoFe蛋白的α和β亚基具有18%和15%的序列同一性。三个亚基的基因vnfD（α）、vnfG（δ）和vnfK（β）是相邻的，并形成一个操纵子，其转录在氨的作用下受到抑制。V固氮酶（Ac2V）的铁蛋白组分是我们先前已克隆和测序的nifH*的产物。该基因位于vnfD上游2.5 kb处。vnfD、G和K基因簇中的缺失会阻止依赖钒的固氮作用。在V固氮酶和Mo固氮酶结构基因均有缺陷的菌株中未显示出残留的固氮能力，这表明该生物体中不存在第三种固氮系统。
