Heteromeric amino acid transporters (HATs) are composed of two subunits, a heavy (SLC3 family) and a light subunit [SLC7 or L-type amino acid transporter (LAT) family]linked by a conserved disulfide bridge []. HATs are amino acid exchangers, and the transport activity resides in the light subunit. The heavy chain of the surface antigen 4F2 (4F2hc), also known as solute carrier family 3 member 2 protein (Slc3a2), is a HAT heavy subunit [, ]. 4F2hc controls the cell surface expression as well as the membrane topology of the 4F2 heterodimer [].
