The protein encoded by this gene is a member of a transmembrane protein family that transports small molecules across membranes. The encoded protein has been found in lysosomal membranes, where it can transport catabolites from the lysosomes to the cytoplasm. This protein has been shown to be an effective transporter of the cytotoxic drug maytansine, which is used in antibody-based targeting of cancer cells. [provided by RefSeq, Dec 2016].