Organic cation transporters belong to the Solute carrier family 22 (SLC22) and the MATE family. The SLC22 family contains the three subtypes of passive diffusion organic cation transporters called OCT1 (SLC22A1), OCT2 (SLC22A2) and OCT3 (SLC22A3). OCT1 is responsible for the uptake of organic cationic compounds from blood to hepatocytes.
Like most members of the SLC22 family, the organic cation and carnitine transporters have a predicted membrane topology that comprises 12 α-helical transmembrane domains (TMDs), an intracellular N-terminus, a large glycosylated extracellular loop, a large intracellular loop with phosphorylation sites and an intracellular C-terminus