title: Molecular model of the neural dopamine transporter.
abstract: The dopamine transporter (DAT) regulates the action of dopamine by reuptake of the neurotransmitter into presynaptic neurons, and is the main molecular target of amphetamines and cocaine. DAT and the Na+/H+ antiporter (NhaA) are secondary transporter proteins that carry small molecules across a cell membrane against a concentration gradient, using ion gradients as energy source. A 3-dimensional projection map of the E. coli NhaA has confirmed a topology of 12 membrane spanning domains, and was previously used to construct a 3-dimensional NhaA model with 12 trans-membrane alpha-helices (TMHs). The NhaA model, and site directed mutagenesis data on DAT, were used to construct a detailed 3-dimensional DAT model using interactive molecular graphics and empiric force field calculations. The model proposes a dopamine transport mechanism involving TMHs 1, 3, 4, 5, 7 and 11. Asp79, Tyr252 and Tyr274 were the primary cocaine binding residues. Binding of cocaine or its analogue, (-)-2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane (CFT), seemed to lock the transporter in an inactive state, and thus inhibit dopamine transport. The present model may be used to design further experimental studies of the molecular structure and mechanisms of DAT and other secondary transporter proteins.
authors.affiliation: Department of Pharmacology, Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway.
authors.forename: Aina Westrheim
authors.initials: AW
authors.lastname: Ravna
authors.forename: Ingebrigt
authors.initials: I
authors.lastname: Sylte
authors.forename: Svein G
authors.initials: SG
authors.lastname: Dahl
mesh_terms: D000465:Algorithms; D000595:Amino Acid Sequence; D003042:Cocaine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D003198:Computer Simulation; D004298:Dopamine / Q000737:chemistry / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; C493214:SLC6A3 protein, human; D014867:Water; C021279:(1R-(exo,exo))-3-(4-fluorophenyl)-8-methyl-8- azabicyclo(3.2.1)octane-2-carboxylic acid, methyl ester; D003042:Cocaine; D004298:Dopamine