Cloning, characterisation and regulation of the ornithine transaminase ( otaA ) gene of Aspergillus nidulans

Abstract

The ornithine transaminase (otaA) gene of Aspergillus nidulans has been cloned by transformation of the A. nidulans pro-ota- mutant strain with a cosmid gene library. The otaA gene contains two introns and potentially codes for a 453-aa-long protein. The deduced amino-acid sequence is homologous to known ornithine transaminases from Saccharomyces cerevisiae, Plasmodium falciparum, Vigna aconitifolia, rat, mouse and man, particularly in the pyridoxal phosphate-binding domain. The expression of the otaA gene is specifically induced by arginine, and is also under the control of nitrogen-metabolite and carbon-catabolite repression. Regulation of the gene occurs at both transcriptional and post-transcriptional levels. The promoter region of otaA contains putative AREA and CREA binding-sites. Fusion proteins containing AREA or CREA DNA-binding domains bind some of these sites. CREA binding-sites correspond very well to the CREA-binding consensus sequence which is SYGGRG. AREA binding-sites are composed of GATT sequences which are not typical binding sites for the GATA - binding family of transcription factors.

Characterization of the oat1 gene of Penicillium chrysogenum encoding an ω-aminotransferase: induction by L-lysine, L-ornithine and L-arginine and repression by ammonium

“…7). This repeat is similar to the core of a 12-bp direct repeat that has been reported to serve as the binding site for a protein involved in the induction of the equivalent otaA gene of A. nidulans by arginine (Dzikowska et al 1999) and may have a similar function in the promoter of the P. chrysogenum gene (see Discussion).…”

“…OAT and LAT activities of the parental Wis 54-1255 strain and the five oat1-deleted mutants. The OAT and LAT activities, assayed using L-ornithine and L-lysine, respectively, as amino group donors, were determined using 2-ketoglutarate as the amino group acceptor Although its closest relatives have been designated as ornithine aminotransferases (Dzikowska et al 1999), the data on the substrate specificity of the purified enzyme (Martı´n de Valmaseda et al 2005), together with the results of the enzyme analysis of the oat1 mutants reported in this paper, provide strong evidence that the P. chrysogenum oat1 gene encodes a protein with ornithine and lysine aminotransferase activities that is involved in the catabolism of lysine and ornithine.…”

The bZIP Transcription Factor MeaB Mediates Nitrogen Metabolite Repression at Specific Loci

“…Furthermore, three adjacent GATT sequence elements are also present in front of the MeaB L start codon. These sequence elements were shown to be AreA binding sites in the promoter of the ornithine transaminase gene in A. nidulans, which is strictly repressed by AreA (11). Consistent with AreA acting as a repressor of meaB L , this transcript was not detected in the ⌬nmr mutant (Fig.…”

arcA, the regulatory gene for the arginine catabolic pathway in Aspergillus nidulans

“…Fig. 3 Alignment the promoter regions of the CAR1 and CAR2 genes from S. cerevisiae (Sumrada and Cooper 1984;Degols 1987) with those of the agaA and otaA genes from A. nidulans (Borsuk et al 1999;Dzikowska et al 1999). Region I, the ®rst homology region, corresponding to box A (Messenguy et al 1991); region II, the second homology region.…”