Paul W, Merrick M
Agricultural and Food Research Council Institute of Plant Science Research, University of Sussex, Brighton, England.
Eur J Biochem. 1989 Jan 2;178(3):675-82. doi: 10.1111/j.1432-1033.1989.tb14497.x.
Active Fe protein of nitrogenase was synthesised in a non-nitrogen fixing organism when Escherichia coli was transformed with a plasmid encoding only two nif-specific genes, nifH and nifM of Klebsiella pneumoniae. Hence proteins NifH and NifM are sufficient to produce active Fe protein in E. coli. K. pneumoniae strains carrying chromosomal nifW- and nifZ- mutations were constructed and shown to be significant C2H2-reducing activity and to grow on N-free plates. Nevertheless, derepressing cultures of the mutant strains had reduced levels of MoFe protein activity, and consequently significantly lower levels of nitrogenase activity, than the nif+ parent strain. NifW and NifZ therefore appear to be involved in the formation or accumulation of active MoFe protein, but are not essential for nitrogen fixation in K. pneumoniae under the conditions tested.
当用仅编码肺炎克雷伯菌两个固氮特异性基因nifH和nifM的质粒转化大肠杆菌时，固氮酶的活性铁蛋白在非固氮生物中得以合成。因此，NifH和NifM蛋白足以在大肠杆菌中产生活性铁蛋白。构建了携带染色体nifW和nifZ突变的肺炎克雷伯菌菌株，结果显示这些菌株具有显著的乙炔还原活性，并且能够在无氮平板上生长。然而，与nif+亲本菌株相比，突变菌株的去阻遏培养物中钼铁蛋白活性水平降低，因此固氮酶活性水平也显著降低。因此，NifW和NifZ似乎参与了活性钼铁蛋白的形成或积累，但在所测试的条件下，它们对于肺炎克雷伯菌的固氮作用并非必不可少。
