Transmembrane 4 L Six Family, Member 18 (TM4SF18)

TM4SF18 also known as AAB5 and L6D, was cloned from human umbilical vein endothelial cells. It shares approximately 40 - 50% amino acid sequence identity with L6, IL-TMP, and TM4SF5, a group of proteins with limited homology to the tetraspanin superfamily.TM4SF18 belongs to the L6 tetraspanin family, L6, IL-TMP, and TM4SF5 are cell surface proteins predicted to have four transmembrane domains. Previous sequence analysis led to their assignment as members of the tetraspanin superfamily. A new sequence (L6D) that is strikingly similar to L6, IL-TMP, and TM4SF5. Analyses of these four sequences indicate that they are not significantly related to genuine tetraspanins, but instead constitute their own L6 superfamily.