LERK-2, A BINDING-PROTEIN FOR THE RECEPTOR-TYROSINE KINASE ELK, IS EVOLUTIONARILY CONSERVED AND EXPRESSED IN A DEVELOPMENTALLY-REGULATED PATTERN

We have isolated and characterized cDNA clones that encode the rat homologue of a binding protein, LERK-2, for the receptor tyrosine kinase, elk. The cDNAs contain an open reading frame of 1527 nucleotides capable of encoding a protein 345 amino acid residues in length. The nucleotide sequence of the present clones is >90% identical to the previously identified human LERK-2 cDNA, and the predicted proteins encoded by the rat and human clones are identical at 95% of amino acid residues. Recombinant proteins expressed from the rat cDNAs bind to elk with high affinity, similar to recombinant human LERK-2 and an endogenously-expressed rat elk-binding protein. Expression of the rat LERK-2 mRNA was detected in embryonic brain, kidney, lung, skeletal muscle, thymus, liver, and heart, and diminished in the early post-natal period. Significant LERK-2 mRNA expression in the young adult rat was restricted to the lung, kidney, heart and testes.