cDNA Cloning and Characterization of a Cek7 Receptor Protein-tyrosine Kinase Ligand That Is Identical to the Ligand (ELF-1) for the Mek-4 and Sek Receptor Protein-tyrosine Kinases

We have isolated a murine cDNA encoding a ligand for the Cek7 receptor protein-tyrosine kinase (RPTK), a member of the Eph/Eck RPTK subfamily. Sequence analysis predicts an open reading frame of 209 amino acids with a predicted molecular mass of 24 kDa. The Cek7 ligand shows a 48% sequence identity at the protein level to B61, a ligand for the related Eck RPTK, 30% to the Cek5 ligand, 59% to the recently cloned Ehk1-L, and identity to ELF-1, a recently described ligand for the Mek4 and Sek RPTKs. The expressed Cek7 ligand is functionally active as it induces autophosphorylation of the Cek7 RPTK.