Sequence similarity of phospholipase C with the non-catalytic region of src

The production of the second messenger molecules diacylglycerol and inositol 1,4,5-trisphosphate is mediated by activated phosphatidylinositol-specific phospholipase C (PLC) enzymes. Here we report the cloning of a bovine brain complementary DNA encoding an enzyme PLC-148 that is characterized by calcium-dependent and phosphatidylinositol-specific phospholipase C activity when expressed in mammalian cells. Bovine brain messenger RNA contains a 7.5-kilobase transcript corresponding to the isolated cDNA; a related transcript of the same size is present in mRNA from some but not all human cell lines tested. Southern blot analysis of the bovine genome indicated that one or possibly two genes hybridize to the cloned PLC-148 cDNA. There is a striking sequence similarity between specific regions of PLC-148 and the non-catalytic domain of the non-receptor tyrosine kinases. The newly characterized crk transforming gene of the avian sarcoma virus CT10 also contains extensive sequence similarities with PLC-148.