xCT: The Membrane's Gatekeeper

xCT is an obligate, electroneutral, membrane-bound anionic transporter responsible for regulating particular amino acid gradients via their transport through plasma membrane. The antiporter xCT superficially resembles an ion channel and preferentially catalyzes the exchange of L-cystine for L-glutamate residues in animal cells. Unlike other glutamate transporters like EAATs, xCT functions independently of an electrochemical sodium ion gradient. xCT is present in most peripheral tissues (heart, bone, liver, and testes).