An intracellular interaction network regulates conformational transitions in the dopamine transporter.

Research output: Contribution to journalJournal articleResearchpeer-review

Neurotransmitter:sodium symporters (NSS)(1) mediate sodium-dependent reuptake of neurotransmitters from the synaptic cleft and are targets for many psychoactive drugs. The crystal structure of the prokaryotic NSS protein, LeuT, was recently solved at high resolution; however, the mechanistic details of regulation of the permeation pathway in this class of proteins remain unknown. Here we combine computational modeling and experimental probing in the dopamine transporter (DAT) to demonstrate the functional importance of a conserved intracellular interaction network. Our data suggest that a salt bridge between Arg-60 in the N terminus close to the cytoplasmic end of transmembrane segment (TM) 1 and Asp-436 at the cytoplasmic end of TM8 is stabilized by a cation-pi interaction between Arg-60 and Tyr-335 at the cytoplasmic end of TM6. Computational probing illustrates how the interactions may determine the flexibility of the permeation pathway, and mutagenesis within the network and results from assays of transport, as well as the state-dependent accessibility of a substituted cysteine in TM3, support the role of this network in regulating access between the substrate binding site and the intracellular milieu. The mechanism that emerges from these findings may be unique to the NSS family, where the local disruption of ionic interactions modulates the transition of the transporter between the outward- and inward-facing conformations.
Original languageEnglish
JournalJournal of Biological Chemistry
Issue number25
Pages (from-to)17691-701
Number of pages10
Publication statusPublished - 2008

Bibliographical note

Keywords: Amino Acid Sequence; Animals; COS Cells; Cercopithecus aethiops; Cytoplasm; Dopamine Plasma Membrane Transport Proteins; Gene Expression Regulation; Humans; Models, Biological; Molecular Sequence Data; Mutagenesis, Site-Directed; Neurotransmitter Agents; Protein Conformation; Sequence Homology, Amino Acid; Sodium

ID: 5772558