A protein with core architecture consisting of asignal sequence, 5 Ig-like domains, followed by a transmembrane sequence, followed by a Protein tyrosine kinase domain (Pfam:PF07714). However, only 1-3 of the Ig domains are detected by the Pfam HMMs in most of the sequences. Pfam:PF00047 is most common, but other members of the Ig domain clan, Pfam:PF07679 and Pfam:PF07686 can be identified instead. The fourth Ig domain lacks the disulfide-bonded cysteines. [ PRO:WCB ]