Unkles S E, Campbell E I, Punt P J, Hawker K L, Contreras R, Hawkins A R, Van den Hondel C A, Kinghorn J R
Plant Molecular Genetics Unit, University of St. Andrews, Fife, U.K.
Gene. 1992 Feb 15;111(2):149-55. doi: 10.1016/0378-1119(92)90682-f.
The Aspergillus niger niaD gene has been sequenced and the inferred nitrate reductase (NR) protein found to consist of 867 amino acid residues (97 kDa). The gene is interrupted by six small introns, as deduced by comparison with the niaD gene of Aspergillus nidulans. The positions of these putative introns are conserved between the two fungi, although the sequences are dissimilar. The niiA gene, encoding nitrite reductase, the second reductive step in the nitrate assimilation pathway, is tightly linked to niaD and divergently transcribed in A. niger, similar to the general organisation in the related fungi, Aspergillus oryzae and A. nidulans. The nucleotide (nt) sequences of the intergenic region between niiA and niaD (excluding the ATG translation start codon) of A. niger (1668 nt) and A. oryzae (1575 nt) were determined and compared with the previously determined A. nidulans (1262 nt) sequence. No striking extended nt regions of homology are observed in spite of the fact that transgenic strains with fungal niaD or the two control genes required for induction and repression show virtually normal regulation. Fungal NR shows considerable aa homology with higher plant NR, particularly within the co-factor domains for flavin adenoside dinucleotide, heme and molybdopterin cofactor.
黑曲霉niaD基因已被测序，推导的硝酸还原酶（NR）蛋白由867个氨基酸残基组成（97 kDa）。通过与构巢曲霉的niaD基因比较推断，该基因被6个小内含子打断。尽管序列不同，但这两种真菌中这些推定内含子的位置是保守的。编码亚硝酸还原酶（硝酸同化途径中的第二步还原反应）的niiA基因与niaD紧密连锁，并在黑曲霉中反向转录，类似于相关真菌米曲霉和构巢曲霉的一般组织形式。测定了黑曲霉（1668 nt）和米曲霉（1575 nt）中niiA和niaD之间基因间区域的核苷酸（nt）序列（不包括ATG翻译起始密码子），并与先前测定的构巢曲霉（1262 nt）序列进行了比较。尽管携带真菌niaD或诱导和抑制所需的两个对照基因的转基因菌株显示出几乎正常的调控，但未观察到明显的长同源核苷酸区域。真菌NR与高等植物NR有相当程度的氨基酸同源性，特别是在黄素腺嘌呤二核苷酸、血红素和钼蝶呤辅因子的辅因子结构域内。
