eek and erk, new members of the eph subclass of receptor protein-tyrosine kinases.

We have identified human and rat DNAs encoding two novel members of the eph subclass of putative receptor protein-tyrosine kinases. Rat cDNA clones encoding eek (eph- and elk-related kinase) were isolated from a brain cDNA library probed with DNA encoding the kinase region of the insulin receptor-related receptor. The predicted eek protein contains all the amino acid residues conserved in the catalytic domains of protein-tyrosine kinases and is most similar to two putative receptor protein-tyrosine kinases of the eph subclass, elk (69%) and eph (57%). Human genomic DNAs encoding part of eek (EEK) as well as another putative protein-tyrosine kinase most similar to elk (90%), ERK (elk-related kinase), were isolated and partially characterized. The novel identity of these two eph-family genes was further supported by Southern blot analyses and localization to human chromosome 1. In Northern blot analysis of rat RNA, DNAs encoding rat eek and human ERK hybridized to transcripts most abundant in brain and lung, respectively. These two new members of the eph subclass of receptor protein-tyrosine kinases, eek and erk, may therefore have tissue-specific functions distinct from those of other eph family members.