Ryk (Related to tyrosine (Y) kinase; also VIK and MRK) is a member of the tyrosine protein kinase family. It is a type I transmembrane glycoprotein that binds Wnt and forms a Wnt receptor complex with Frizzled. In this capacity, Ryk serves as a link between Wnt and Dishevelled.
Human Ryk is 604 amino acids (aa) in length. It contains a 25 aa signal sequence and a 199 aa extracellular region (aa 26 - 224) that shows one WIF-1-like domain (aa 63 - 191). The cytoplasmic region of Ryk possesses a nonfunctional Ser/Thr protein kinase domain (aa 327 - 600). One isoform exists that shows a 31 aa substitution between aa 18 - 46. Over aa 47 - 224, human Ryk is 94% aa identical to mouse Ryk.