RT Journal Article SR Electronic T1 Importance of Valine at Position 152 for the Substrate Transport and 2β-Carbomethoxy-3β-(4-fluorophenyl)tropane Binding of Dopamine Transporter JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 883 OP 889 VO 57 IS 5 A1 Sang-Hun Lee A1 Mi-yoon Chang A1 Ki-Hwan Lee A1 Byung Sup Park A1 Young-Seek Lee A1 Hemin R. Chin A1 Yong-Sung Lee YR 2000 UL http://molpharm.aspetjournals.org/content/57/5/883.abstract AB Human and bovine dopamine transporters (DAT) demonstrate discrete functional differences in dopamine (DA), 1-methyl-4-phenylpyridium (MPP+) transport, and cocaine analog binding. In a previous study, the functional analyses on the chimeras of human and bovine DAT have revealed that the region from residues 133 through 186 (encompassing the third transmembrane domain) is responsible for the substrate transport and cocaine analog binding. The present study has been carried out to determine the specific amino acid(s) conferring DAT functions by interchanging the amino acid residues in the corresponding region between human and bovine DAT. As described previously, the DA, MPP+ transport, and 2β-carbomethoxy-3β-(4-fluorophenyl)tropane (CFT) binding almost disappeared in chimera hb3 in which the region from residues 133 through 186 of bovine DAT was substituted into human DAT. Replacement of isoleucine, residue 152 of chimera hb3 (bovine DAT sequence), with valine, the human DAT residue at the identical position, remarkably restored the substrate transport and CFT binding to 76% to 98% of the human DAT values. Similarly, substitution of isoleucine for valine at position 152 in the human DAT reduced the substrate transport and CFT binding by 57% to 97%. Among other amino acids tested at position 152 of the chimera hb3, only alanine resulted in small but significant increases in the DAT functions ranging from 16 to 34%. Thus, valine at position 152 plays a crucial role for molecular mechanisms underlying the interactions of DA, MPP+, and CFT with human DAT. The American Society for Pharmacology and Experimental Therapeutics