Molecular analysis of the argB gene of Aspergillus nidulans

The transcriptional organization and sequence of the Aspergillus nidulans argB gene, encoding ornithine carbamoyl transferase (OCTase; E.C. 2.1.3.3.), was determined. Transcription of the gene begins within a methionine-initiated open translation reading frame, indicating that a second methionine codon of the open reading frame is used for translation initiation. The predicted length of the OCTase precursor peptide is 359 amino acids, and it contains a highly basic amino terminus that is probably involved in mitochondrial targeting. There is extensive homology between Aspergillus OCTase and mammalian and bacterial OCTases and weaker homology between the Aspergillus polypeptide and bacterial arginine carbamoyl transferase.