Importance of Valine at Position 152 for the Substrate Transport and 2β-Carbomethoxy- 3β-(4-fluorophenyl)tropane Binding of Dopamine TransporterImportance of Valine at Position 152 for the Substrate Transport and 2-Carbomethoxy- 3-(4-fluorophenyl)tropane Binding of Dopamine TransporterImportance of Valine at Position 152 for the Substrate Transport and 2b-carbomethoxy-3b-(4-fluorophenyl)tropane Binding of Dopamine Transporter