Polyphosphoinositide synthesis and protein phosphorylation in the plasma membrane from full-grown Bufo arenarum oocytes.

1. Polyphosphoinositide content and phosphorylation of lipids and proteins were analyzed in oocytes of the toad Bufo arenarum Hensel. 2. Plasma membrane-enriched fractions obtained from full-grown, prophase-arrested oocytes incorporated 32P into both phospholipids and proteins after incubation with gamma-32P]ATP in an Mg(2+)-containing medium. Phosphatidylinositol 4-phosphate (PIP), phosphatidate (PA) and phosphatidylinositol-4,5-bisphosphate (PIP2) were the only labelled lipids. The 32P incorporation depended on incubation time, the amount of protein, and the ATP concentration. 3. Autoradiography of polyacrylamide gel electropherograms and scintillation counting showed that the radioactivity was mainly associated with a group of membrane proteins having an M(r) of 87,000. 4. This paper provides evidence for the capacity of prophase-arrested oocytes from Bufo arenarum to synthesize polyphosphoinositides and to phosphorylate distinct membrane proteins.