Two human 35 kd inhibitors of phospholipase A sub(2) are related to substrates of pp60 super(v-src) and of the epidermal growth factor receptor/kinase

The authors have purified two 35 kd phospholipase A sub(2) inhibitors from human placenta, which they refer to as lipocortin I and II. Both proteins exhibit similar biochemical properties and occur in placenta at about 0.2% of the total protein. By peptide mapping, sequence, and immunological analyses, they show that lipocortin I and the 35 kd substrate for the EGF-receptor/kinase from A431 cells are the same protein. By similar criteria, they determine that lipocortin II is the human analogue of pp36, a major substrate for pp60 super(src), which has been characterized in chicken embryo fibroblasts and in bovine brush border preparations. The amino acid sequences of lipocortin I and II that they deduced from cDNA clones share 50% homology, indicatiing that they probably evolved from a common gene.