Physical characterization of the aldehyde-dehydrogenase-encoding gene of Aspergillus niger

To facilitate a better understanding of the regulation of aldA, the gene encoding aldehyde dehydrogenase (AldDH) in the ascomyeete fungus, Aspergillus niger, the gene has been physically characterized. The complete nucleotide (nt) sequence of the gene and its flanking regions has been determined. Analysis of the gene has revealed the presence of three introns. The homologous gene in the related fungus, Aspergillus nidulans, contains only two introns. The coding regions of these genes, excluding the intron sequences, show 80% homology at the nt level and 82% homology at the amino acid (aa) level. The aa sequence of the A. niger enzyme is significantly homologous to mammalian sequences, particularly around one Cys residue, which is hypothesized to be adjacent to another Cys known to be at the active site of mammalian AldDHs. The 5' region of the gene shows one major and two minor transcription start points and a general structure common to highly expressed fungal genes. The 3' region shows four sites of polyadenylation. Sequence comparisons of the 5' region of the A. niger aldA gene to other Aspergillus genes has shown a common sequence in the 5' regions of several A. nidulans genes, all but one of which are subject to carbon catabolite repression. This sequence may be important for the regulatory mechanism.