GROWTH OF A MUTANT DEFECTIVE IN A PUTATIVE PHOSPHOINOSITIDE-SPECIFIC PHOSPHOLIPASE-C OF SCHIZOSACCHAROMYCES-POMBE IS RESTORED BY LOW CONCENTRATIONS OF PHOSPHATE AND INOSITOL

A mutant (plc1-1) of Schizosachar omyces pombe unable to grow on a minimal medium containing high amounts of phosphate was selected. On yeast-extract agar its growth is temperature sensitive. Tests in liquid synthetic medium show that growth of the mutant is partially restored by lowering the phosphate and inositol concentrations in the growth medium. The growth defect is fully suppressed by a plasmid encoding a putative protein having the structural features of phosphoinositide-specific phospholipases C (PI-PLC). This protein, of 899 amino-acids, contains the characteristic X and Y domains found in all PI-PLCs of higher and lower eucaryotes and reveals, in addition, an EF-hand motif (putative Ca2+-binding site). Like the corresponding enzyme from Saccharomyces cerevisiae, the S. pombe PI-PLC is most similar-to the delta form of PI-PLC isoenzymes. The cloned gene integrates at the plc1 site indicating that plc1 codes for a putative PI-PLC. Plc1 physically maps on the left arm of chromosome II between rad11 and mei3.