Aguilar O M, Taormino J, Thöny B, Ramseier T, Hennecke H, Szalay A A
Plant Molecular Genetics and Biotechnology Center, University of Alberta, Edmonton, Canada.
Mol Gen Genet. 1990 Dec;224(3):413-20. doi: 10.1007/BF00262436.
The nucleotide sequences of genes homologous to the Klebsiella pneumoniae nifEN genes have been determined in Bradyrhizobium japonicum 110. The coding regions for the nifE and nifN consist, respectively, of 1641 and 1407 nucleotides. The nifD gene (coding for the beta-subunit of dinitrogenase) and nifE are linked, and separated by 95 nucleotides. In the region of 12 nucleotides that separates nifE from nifN the stop codon for nifE overlaps the putative ribosome binding site for nifN. In contrast to Klebsiella and Azotobacter vinelandii, the B. japonicum nifEN genes are linked to the nifDK genes in the same operon. Comparison of dinitrogenase polypeptides (nifDK products) and the polypeptides of the nifE and nifN genes reveals considerable homology between nifD and nifE, and between nifK and nifN. Several protein domains, containing highly conserved cysteine residues, are conserved among the gene products of nifD, nifK, nifE and nifN. This result allows us to propose a probable evolutionary pathway for the common origin of these genes.
已测定了慢生根瘤菌110中与肺炎克雷伯氏菌nifEN基因同源的基因的核苷酸序列。nifE和nifN的编码区分别由1641和1407个核苷酸组成。nifD基因（编码固氮酶的β亚基）与nifE相连，间隔95个核苷酸。在将nifE与nifN隔开的12个核苷酸区域中，nifE的终止密码子与nifN的推定核糖体结合位点重叠。与克雷伯氏菌和棕色固氮菌不同，慢生根瘤菌的nifEN基因与nifDK基因位于同一个操纵子中。对固氮酶多肽（nifDK产物）以及nifE和nifN基因的多肽进行比较，发现nifD与nifE之间以及nifK与nifN之间存在相当程度的同源性。在nifD、nifK、nifE和nifN的基因产物中，有几个包含高度保守半胱氨酸残基的蛋白质结构域是保守的。这一结果使我们能够提出这些基因共同起源的可能进化途径。
