CDNA CLONING AND CHARACTERIZATION OF A CEK7 RECEPTOR PROTEIN-TYROSINEKINASE 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 subfamil y. 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 rela ted 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 ind uces autophosphorylation of the Cek7 RPTK.