RYK is an atypical member of the family of growth factor receptor protein tyrosine kinases, differing from other members at a number of conserved residues in the activation and nucleotide binding domains. This gene product belongs to a subfamily whose members do not appear to be regulated by phosphorylation in the activation segment. It has been suggested that mediation of biological activity by recruitment of a signaling-competent auxiliary protein may occur through an as yet uncharacterized mechanism. A nine nucleotide insertion in some transcripts results in the SLG variant. It is not established whether this is a product of alternative splicing or a second gene, since evidence for a second gene or pseudogene on chromosome 17 exists.