The SLC16A gene family encode proton-linked monocarboxylate transporters (MCT) which mediate the transport of monocarboxylates such as lactate and pyruvate. Monocarboxylates are a major energy source for all cells in the body so their transport in and out of cells is crucial for cellular function. To date, 14 SLC16A members have been identified through sequence homology. Of these 14 members, only seven isoforms have been functionally characterized and not all of these function as proton-coupled transporters. A number can transport diuretics, thyroid hormones and aromatic amino acids. The seven remaining SLC16A members are classed as orphan MCTs (Morris & Felmlee 2008, Merezhinskaya & Fishbein 2009).
In mammalian cells, MCTs (monocarboxylate transporters) require association with an ancillary protein to enable plasma membrane expression of the active transporter. Basigin (BSG, CD147) is the preferred binding partner for MCT1, MCT3 and MCT4, while MCT2 requires Embigin (EMB) (Wilson et al. 2005).