STRUCTURAL RELATIONSHIP BETWEEN A BACTERIAL DEVELOPMENTAL PROTEIN ANDEUKARYOTIC PP2C PROTEIN PHOSPHATASES

Bacillus subtilis SpollE is a Ser protein phosphatase whose action on the phosphoprotein SpollAA triggers the cell type-specific activation of a sporulation transcription factor. Here we report that SpollE disp lays sequence similarity to the PP2C family of eukaryotic Ser/Thr prot ein phosphatases, and that residues common to these proteins are requi red for the function of both SpollE and TPD1, a yeast PP2C. These find ings suggest that SpollE and the PP2C protein phosphatases are structu rally related, and reveal a striking formal similarity between the Spo llAA regulatory circuit and that of mammalian mitochondrial pyruvate d ehydrogenase. This similarity may reflect an evolutionarily conserved mechanism of biological regulation based on the interplay of His prote in kinaselike Ser kinases and PP2C-like protein phosphatases.