Background
Monocarboxylates, such as lactate and pyruvate, play an integral role in cellular metabolism. Lactic acid is produced in large quantities as a result of glycolysis, which provides the majority of ATP to cells under normal physiological conditions. However, accumulation of lactic acid leads to a decrease in intracellular pH and, thus, to a cessation of glycolysis. In order for glycolysis to continue at a high rate, lactic acid must be transported out of the cell. This transport process is carried out by a family of monocarboxylate transporters (MCTs), which function as proton symports and are stereoselective for L-lactate. MCT13 (Monocarboxylate transporter 13), also known as SLC16A13 (Solute carrier family 16 member 13), is a 426 amino acid multi-pass membrane protein that belongs to the MCT transport family. Functioning as a proton-linked monocarboxylate transporter, MCT13 catalyzes the rapid transports of molecules, such as lactate, across the plasma membrane.