2Q72

Crystal Structure Analysis of LeuT complexed with L-leucine, sodium, and imipramine

2Q72 の概要

• エントリーDOI: 10.2210/pdb2q72/pdb
• 関連するPDBエントリー: 2A65 2Q6H 2QB4 2QEI
• 分子名称: Transporter, octyl beta-D-glucopyranoside, SODIUM ION, ... (6 entities in total)
• 機能のキーワード: membrane protein, neurotransmitter sodium symporter, occluded, tricyclic antidepressant, transport protein
• 由来する生物種: Aquifex aeolicus
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 60277.25

構造登録者

Singh, S.K.,Yamashita, A.,Gouaux, E. (登録日: 2007-06-05, 公開日: 2007-08-21, 最終更新日: 2023-08-30)

主引用文献

Singh, S.K.,Yamashita, A.,Gouaux, E.
Antidepressant binding site in a bacterial homologue of neurotransmitter transporters.
Nature, 448:952-956, 2007

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 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.

PubMed: 17687333
DOI: 10.1038/nature06038

実験手法

X-RAY DIFFRACTION (1.7 Å)