Probing the active center of the mitochondrial dicarboxylate transporter

2-n-Alkylmalonates with various length of the alkyl residue have been used to study the topography of the active center of the dicarboxylate transporter in intact rat liver mitochondria. Measurements of the Ki values of these competitive inhibitors suggest that in the transporter there is a large hydrophobic region at least 1.7 nm in size, containing a polar domain (ca. 0.5 nm) and situated close to a substrate-binding site. These zones are assumed to be involved in the mechanism of dicarboxylate transport.