4F2 cell-surface antigen heavy chain is a protein that in humans is encoded by the SLC3A2 (solute carrier family 3 member 2) gene. SLC3A2 comprises the light subunit of the large neutral amino acid transporter (LAT1) that is also known as CD98 (cluster of differentiation 98). This gene is a member of the solute carrier family and encodes a cell surface, transmembrane protein. The protein exists as the heavy chain of a heterodimer, covalently bound through di-sulfide bonds to one of several possible light chains. The encoded transporter plays a role in regulation of intracellular calcium levels and transports L-type amino acids. Alternatively spliced transcript variants, encoding different isoforms, have been characterized. [provided by RefSeq].