Epitopes described in "X-ray structures of LeuT in substrate-free outward-open and apo inward-open states."

Article Authors:Harini Krishnamurthy; Eric Gouaux
Article Title:X-ray structures of LeuT in substrate-free outward-open and apo inward-open states.
Reference Detail
Reference ID:1024762
Abstract:Neurotransmitter sodium symporters are integral membrane proteins that remove chemical transmitters from the synapse and terminate neurotransmission mediated by serotonin, dopamine, noradrenaline, glycine and GABA (-aminobutyric acid). Crystal structures of the bacterial homologue, LeuT, in substrate-bound outward-occluded and competitive inhibitor-bound outward-facing states have advanced our mechanistic understanding of neurotransmitter sodium symporters but have left fundamental questions unanswered. Here we report crystal structures of LeuT mutants in complexes with conformation-specific antibody fragments in the outward-open and inward-open states. In the absence of substrate but in the presence of sodium the transporter is outward-open, illustrating how the binding of substrate closes the extracellular gate through local conformational changes: hinge-bending movements of the extracellular halves of transmembrane domains 1, 2 and 6, together with translation of extracellular loop 4. The inward-open conformation, by contrast, involves large-scale conformational changes, including a reorientation of transmembrane domains 1, 2, 5, 6 and 7, a marked hinge bending of transmembrane domain 1a and occlusion of the extracellular vestibule by extracellular loop 4. These changes close the extracellular gate, open an intracellular vestibule, and largely disrupt the two sodium sites, thus providing a mechanism by which ions and substrate are released to the cytoplasm. The new structures establish a structural framework for the mechanism of neurotransmitter sodium symporters and their modulation by therapeutic and illicit substances.
Affiliations:Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, USA.
Reference Type:Literature
PubMed ID:22230955
Journal Volume:481
Article Pages:469-74
Journal ISSN:1476-4687
Article Chemical List:Antibodies, Monoclonal;Apoproteins;Bacterial Proteins;Immunoglobulin Fab Fragments;Ions;Sodium
Article MeSH List:Animals; Antibodies, Monoclonal(immunology); Antibody Specificity(immunology); Apoproteins(chemistry; genetics; immunology; metabolism); Bacterial Proteins(chemistry; genetics; immunology; metabolism); Binding Sites; Crystallography, X-Ray; Immunoglobulin Fab Fragments(immunology); Ions(chemistry); Models, Molecular; Movement; Protein Conformation; Sodium(chemistry; metabolism); Structure-Activity Relationship; Substrate Specificity
Curation Last Updated:2015-06-07 20:16:30