Multiple mRNAs code for proteins related to the BEK fibroblast growth factor receptor.

The BEK transmembrane protein tyrosine kinase is a receptor for both acidic and basic fibroblast growth factors. We identify several different transcripts which code for BEK-related proteins. These proteins differ from BEK in regions expected to control receptor activity. Thus, some of the proteins have altered extracellular, ligand-binding domains, and others an altered carboxy-terminal tail. Still other forms of BEK differ only in their juxtamembrane domains. Sequencing of parts of the BEK gene shows that alternative splicing of the premessenger can account for at least some of this diversity. In particular, an apparently tissue specific, mutually exclusive splicing of two internal exons permits both the previously described K-SAM mRNA and the BEK mRNA to be derived from the same premessenger.