A novel group IIA phospholipase A(2) interacts with v-Src oncoprotein fromRSV-transformed hamster cells

We have isolated a novel isoform of phospholipase A(2). This enzyme was des ignated srPLA(2) because it was discovered while analyzing the proteins int eracting with different forms of the v-Src oncoproteins isolated from Rous sarcoma virus-transformed hamster cells. It contains all the functional reg ions of the PLA(2) group IIA proteins but differs at its C-terminal end whe re there is an additional stretch of 8 amino acids. The SrPLA(2) isoform wa s detected as a 17-kDa precursor in cells and as a mature 14-kDa form secre ted in culture medium. A direct interaction of the 17-kDa precursor with th e Src protein was observed in lysates of transformed cells. Both the 17- an d 14-kDa forms were found to be phosphorylated on tyrosine. To our knowledg e, this is the first report of a PLA(2) group II protein that is tyrosine p hosphorylated. We surmise that srPLA(2) interacts with the Src protein at t he cell membrane during the process of its maturation.