The 67-kDa calelectrin is the largest member of a family of Ca2"-binding proteins that associate with membranes and phospholipids in a Ca2+-dependent manner.Oligonucleotide probes based on peptide sequences obtained from purified bovine 67-kDa calelectrin were used to screen a human retina cDNA library, and the complete primary structure of human 67-kDa calelectrin was deduced by DNA sequence analysis. Lipocortin I and II are two related proteins each containing four similar repeats. Lipocortin I and II were identified by their ability to inhibit phospholipase A2 activity and were purified using this inhibition as an assay (6, 7). Unexpectedly, when their amino acid sequences were deduced from the nucleotide sequence of cDNA clones, their sequences were found identical to the amino acid sequences of two intracellular protein-tyrosine kinase substrates of 35 kDa and 36 kDa (named p35 and p36, respectively), the primary structure of which was being determined concomitantly (5-9). p35 and p36 appear to be physiological intracellular substrates for pp6v-src and the epidermal growth factor receptor protein-tyrosine kinase (8,9). Although several hypotheses on the function of lipocortin I and II (p35 and p36, respectively) have been advanced, their biological role is still controversial.We report the cDNA cloning and primary structure of the human 67-kDa calelectrin,l the largest member of the cale-