The gene and the primary structure of ornithine decarboxylase from Saccharomyces cerevisiae.

The nucleotide sequence was determined for a 3-kilobase genomic fragment containing the ornithine decarboxylase gene of Saccharomyces cerevisiae. The fragment contained two open reading frames. Gene disruption localized the ornithine decarboxylase gene to a 1398-nucleotide open reading frame. Transcription of the yeast gene initiated at several sites 171 to 211 nucleotides 5' of the translational start site. The 3' end of the transcript extended approximately 300 nucleotides beyond the end of the ornithine decarboxylase coding region and contained two copies of the yeast ARS core sequence. Translation of the ornithine decarboxylase gene appeared to initiate at the first AUG condon of the open reading frame based upon translational fusions with the Escherichia coli beta-galactosidase gene. Since no introns were apparent, the 1398-nucleotide open reading frame was predicted to encode a 466-amino acid protein with a calculated Mr = 52,369. The deduced protein differed significantly in size from previous reports on yeast ornithine decarboxylase, but was very similar in size to mammalian ornithine decarboxylase. When the predicted amino acid sequence of yeast ornithine decarboxylase was compared with that of the mouse enzyme, alignment of the sequences revealed that 40% of the amino acid residues were identical. Chou-Fasman predictions of the secondary structure of the two enzymes indicated that secondary structure was also highly conserved.