X-ray structures of LeuT in substrate-free outward-open and apo inward-open states

Harini Krishnamurthy, Eric Gouaux

Research output: Contribution to journalArticle

310 Citations (Scopus)

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 (γ-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.

Original languageEnglish (US)
Pages (from-to)469-474
Number of pages6
JournalNature
Volume481
Issue number7382
DOIs
StatePublished - Jan 26 2012

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Plasma Membrane Neurotransmitter Transport Proteins
X-Rays
Sodium
Aminobutyrates
Bacterial Structures
Immunoglobulin Fragments
Synaptic Transmission
Synapses
Glycine
gamma-Aminobutyric Acid
Dopamine
Serotonin
Norepinephrine
Membrane Proteins
Cytoplasm
Ions

ASJC Scopus subject areas

  • General

Cite this

X-ray structures of LeuT in substrate-free outward-open and apo inward-open states. / Krishnamurthy, Harini; Gouaux, Eric.

In: Nature, Vol. 481, No. 7382, 26.01.2012, p. 469-474.

Research output: Contribution to journalArticle

Krishnamurthy, Harini ; Gouaux, Eric. / X-ray structures of LeuT in substrate-free outward-open and apo inward-open states. In: Nature. 2012 ; Vol. 481, No. 7382. pp. 469-474.
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