Plexin This is a cysteine rich repeat found in several different extracellular receptors. The function of the repeat is unknown. Three copies of the repeat are found in plexin (<db_xref db="SWISSPROT" dbkey="P70206"/>) [<cite idref="PUB00004313"/>]. Two copies of the repeat are found in mahogany protein. A related <taxon tax_id="6239">Caenorhabditis elegans</taxon> protein (<db_xref db="SWISSPROT" dbkey="Q19981"/>) contains four copies of the repeat, while the Met receptor contains a single copy of the repeat.