Polyspecific organic cation transport: insights into the substrate binding site.

Positively charged endogenous and exogenous organic compounds of diverse chemical structures are transported by polyspecific organic cation transporters (OCT). In two contributions to the May 2005 issue of Molecular Pharmacology, amino acid residues within the fourth and tenth transmembrane helices of rat OCT1 are described that contribute to cation and corticosterone binding. In a three-dimensional model based on the structure of the lactose permease, these residues are located in a large grove, the binding site for biogenic amines and cationic drugs.