SERINC4 (serine incorporator 4) is a 518 amino acid multi-pass membrane protein that belongs to the TDE1 family. The SERINC4 protein Incorporates a polar amino acid serine into membranes and facilitates the synthesis of two serine-derived lipids, phosphatidylserine and sphingolipids. Because SERINC proteins contain 11 transmembrane segments resembling amino acid transporters, SERINC4 may also function as an L-serine transporter by carrying serine molecules into the hydrophobic milieu of membrane lipid bilayers.