The search for the biological function of novel yeast Ser/Thr phosphatases

The genome of the yeast S. cerevisiae contains a fairly large number of genes encoding Ser/Thr protein phosphatases. Among these genes can be found the homologs of the classical phosphatases described in mammalian tissues in the early 1980s. For instance, the catalytic subunit of PP1 is encoded by the gene GLC7, whereas two forms of PP2A are encoded by genes PPH21 and PPH22. As it happens in other organisms, the yeast catalytic subunits of PP1, PP2A, and PP2B (calcineurin) are quite related in sequence. In addition to these phosphatases, yeast cells contain other phosphatase genes that, while related to PP1 or PP2A in their primary structure, are functionally different. The main features of these genes (1–13) are described in Table 1.