Structural characteristics of the PHO8 gene encoding repressible alkaline phosphatase in Saccharomyces cerevisiae

The nucleotide sequence of a 3694-bp DNA fragment bearing the PHO8 gene encoding nonspecific repressible alkaline phosphatase (rALPase; EC 3.1.3.1) of Saccharomyces cerevisiae was determined. The sequence contains a 1698 bp open reading frame (ORF), and the major PHO8 transcription start point at 32 bp upstream from the ATG codon; several minor transcription start points are located between the major start point and ATG. The major start point is most responsive to the phosphate signals. The amino acid (aa) sequence deduced from the ORF contains several homologous regions in common with alkaline phosphatases of Escherichia coli and human placenta. A PHO8 DNA fragment previously isolated [Kaneko et al., Mol. Cell. Biol. 5 (1985) 248-252] was found to be truncated for the region encoding the 22 aa residues at the C terminus of the enzyme, which were replaced with 17 aa encoded by a pBR322 DNA. The modified gene could produce significant rALPase activity without the function of proteinase A which is required for the maturation of rALPase from its precursor.