Carland, Jane EThomas, MichaelMostyn, ShannonSubramanian, NandhithaO'Mara, MeganRyan, Renae M.Vandenberg, Robert J2021-08-111948-7193http://hdl.handle.net/1885/243871Transporters in the SLC6 family play key roles in regulating neurotransmission and are the targets for a wide range of therapeutics. Important insights into the transport mechanisms and the specificity of drug interactions of SLC6 transporters have been obtained from the crystal structures of a bacterial homologue of the family, LeuTAa, and more recently the Drosophila dopamine transporter and the human serotonin transporter. However, there is disputed evidence that the bacterial leucine transporter, LeuTAa, contains two substrate binding sites that work cooperatively in the mechanism of transport, with the binding of a second substrate being required for the release of the substrate from the primary site. An alternate proposal is that there may be low affinity binding sites that serve to direct the flow of substrates to the primary site. We have used a combination of molecular dynamics simulations of substrate interactions with a homology model of GlyT2, together with radiolabeled amino acid uptake assays and electrophysiological analysis of wild-type and mutant transporters, to provide evidence that substrate selectivity of GlyT2 is determined entirely by the primary substrate binding site and, furthermore, if a secondary site exists then it is a low affinity nonselective amino acid binding site.This work was supported by a National Health and Medical Research Council Project Grant (APP1082570) and the Merit Allocation Scheme on the NCI National Facility at the ANU. M.L.O. is supported by an ARC DECRA (DE120101550). S.M. is supported by an Australian Postgraduate Award.application/pdfen-AU© 2017 American Chemical SocietyNeurotransmitter transportglycineGlyTLeuTAaSLC6 familyNa+ dependence201710.1021/acschemneuro.7b004072020-11-23