Transmembrane proteins contain transmembrane domains that are usually characterized by alpha-helical structures. Transmembrane proteins exist as thermodynamically stable hetero- and homodimers that interact with the lipid bilayer and are involved in both material exchange and communication between the cell and the environment. PL6 is a 351 amino acid multi-pass membrane protein that is highly expressed in kidney and skeletal muscle with lower levels of expression detected in liver, placenta, prancreas, lung, heart and brain. PL6 contains one phosphoserine residue and several transmembrane domains, suggesting that it may participate in protein exchange and signaling events between cells.