Mer and Tyro3 are two members of the TAM family receptor tyrosine kinase that share a common NCAM (neural adhesion molecule)-related extracellular domain and a conserved intracellular tyrosine kinase domain. These receptors bind common homologous vitamin K dependent protein GAS6 and protein S to activate downstream signaling pathways. Members of this family have a common molecular structure which contains an N-terminal extracellular domain comprised of two Ig domains, two FNIII domains and a membrane spanning single helix followed by the cytoplasmic tyrosine kinase domain. These RTKs are functionally significant in spermatogenesis, immunoregulation and phagocytosis. Tyro3, Mer are widely expressed in adult tissues with their expression most abundant in brain, testis, lymphatic and vascular tissue. Tyro3 has been shown to undergo posttranslational modifications including both tyrosine phosphorylation as well as glycosylation.