<p>Ephrins are a family of proteins [<cite idref="PUB00004495"/>] that are ligands of class V (EPH-related) receptor protein-tyrosine kinases (see <db_xref db="INTERPRO" dbkey="IPR001426"/>). These receptors and their ligands have been implicated in regulating neuronal axon guidance and in patterning of the developing nervous system and may also serve a patterning and compartmentalisation role outside of the nervous system as well.</p><p>Ephrins are membrane-attached proteins of 205 to 340 residues. Attachment appears to be crucial for their normal function. Type-A ephrins are linked to the membrane via a glycosylphosphatidylinositol (GPI)-linkage, while type-B ephrins are type-I membrane proteins.</p>