MPP+ (1-methyl-4-phenylpyridinium), a dopaminergic neurotoxin that provides the best available experimental model of Parkinson's disease, is selectively concentrated in dopamine neurons by the dopamine transporter (DAT). DAT also serves as a primary recognition site for cocaine. To help define selective molecular mechanisms by which MPP+ uptake occurs, we have tested dopamine transporters mutated in several residues for their abilities to accumulate dopamine and MPP+, and to bind a cocaine analog. Mutants in DAT 7th and 11th hydrophobic putative transmembrane domains increase MPP+ uptake velocity and affinity (1/KD), respectively. These mutations exert much more modest effects on dopamine uptake and have little impact on cocaine analog binding. These findings provide the first example of mutations that enhance transport and identify specific DAT amino acids selectively involved in neurotoxin uptake. They may also have implications for the feasibility of developing drugs that could specifically block accumulation of Parkinsonism-inducing neurotoxins.