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

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.