2QEI

Crystal structure analysis of LeuT complexed with L-alanine, sodium, and clomipramine


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.85 Å
  • R-Value Free: 0.210 
  • R-Value Work: 0.195 
  • R-Value Observed: 0.195 

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Ligand Structure Quality Assessment 


This is version 1.2 of the entry. See complete history


Literature

Antidepressant binding site in a bacterial homologue of neurotransmitter transporters.

Singh, S.K.Yamashita, A.Gouaux, E.

(2007) Nature 448: 952-956

  • DOI: 10.1038/nature06038
  • Primary Citation of Related Structures:  
    2Q6H, 2Q72, 2QB4, 2QEI

  • PubMed Abstract: 
  • Sodium-coupled transporters are ubiquitous pumps that harness pre-existing sodium gradients to catalyse the thermodynamically unfavourable uptake of essential nutrients, neurotransmitters and inorganic ions across the lipid bilayer. Dysfunction of these integral membrane proteins has been implicated in glucose/galactose malabsorption, congenital hypothyroidism, Bartter's syndrome, epilepsy, depression, autism and obsessive-compulsive disorder ...

    Sodium-coupled transporters are ubiquitous pumps that harness pre-existing sodium gradients to catalyse the thermodynamically unfavourable uptake of essential nutrients, neurotransmitters and inorganic ions across the lipid bilayer. Dysfunction of these integral membrane proteins has been implicated in glucose/galactose malabsorption, congenital hypothyroidism, Bartter's syndrome, epilepsy, depression, autism and obsessive-compulsive disorder. Sodium-coupled transporters are blocked by a number of therapeutically important compounds, including diuretics, anticonvulsants and antidepressants, many of which have also become indispensable tools in biochemical experiments designed to probe antagonist binding sites and to elucidate transport mechanisms. Steady-state kinetic data have revealed that both competitive and noncompetitive modes of inhibition exist. Antagonist dissociation experiments on the serotonin transporter (SERT) have also unveiled the existence of a low-affinity allosteric site that slows the dissociation of inhibitors from a separate high-affinity site. Despite these strides, atomic-level insights into inhibitor action have remained elusive. Here we screen a panel of molecules for their ability to inhibit LeuT, a prokaryotic homologue of mammalian neurotransmitter sodium symporters, and show that the tricyclic antidepressant (TCA) clomipramine noncompetitively inhibits substrate uptake. Cocrystal structures show that clomipramine, along with two other TCAs, binds in an extracellular-facing vestibule about 11 A above the substrate and two sodium ions, apparently stabilizing the extracellular gate in a closed conformation. Off-rate assays establish that clomipramine reduces the rate at which leucine dissociates from LeuT and reinforce our contention that this TCA inhibits LeuT by slowing substrate release. Our results represent a molecular view into noncompetitive inhibition of a sodium-coupled transporter and define principles for the rational design of new inhibitors.


    Related Citations: 
    • Crystal structure of a bacterial homologue of Na+/Cl--dependent neurotransmitter transporters
      Yamashita, A., Singh, S.K., Kawate, T., Jin, Y., Gouaux, E.
      (2005) Nature 437: 215

    Organizational Affiliation

    The Vollum Institute, Oregon Health and Science University, 3181 S.W. Sam Jackson Road, Portland, Oregon 97239, USA.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
TransporterA519Aquifex aeolicus VF5Mutation(s): 0 
Gene Names: snfaq_2077
Membrane Entity: Yes 
UniProt
Find proteins for O67854 (Aquifex aeolicus (strain VF5))
Explore O67854 
Go to UniProtKB:  O67854
Protein Feature View
Expand
  • Reference Sequence
Small Molecules
Binding Affinity Annotations 
IDSourceBinding Affinity
CXX Binding MOAD:  2QEI IC50: 5000 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.85 Å
  • R-Value Free: 0.210 
  • R-Value Work: 0.195 
  • R-Value Observed: 0.195 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 89.787α = 90
b = 86.027β = 95.98
c = 81.659γ = 90
Software Package:
Software NamePurpose
CNSrefinement
ADSCdata collection
HKL-2000data reduction
HKL-2000data scaling
CNSphasing

Structure Validation

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Ligand Structure Quality Assessment  



Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2007-08-21
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Derived calculations, Source and taxonomy, Version format compliance
  • Version 1.2: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Data collection, Database references, Derived calculations, Structure summary