ジャーナル: EMBO J / 年: 2022 タイトル: The ion-coupling mechanism of human excitatory amino acid transporters. 著者: Juan C Canul-Tec / Anand Kumar / Jonathan Dhenin / Reda Assal / Pierre Legrand / Martial Rey / Julia Chamot-Rooke / Nicolas Reyes / 要旨: Excitatory amino acid transporters (EAATs) maintain glutamate gradients in the brain essential for neurotransmission and to prevent neuronal death. They use ionic gradients as energy source and co- ...Excitatory amino acid transporters (EAATs) maintain glutamate gradients in the brain essential for neurotransmission and to prevent neuronal death. They use ionic gradients as energy source and co-transport transmitter into the cytoplasm with Na and H , while counter-transporting K to re-initiate the transport cycle. However, the molecular mechanisms underlying ion-coupled transport remain incompletely understood. Here, we present 3D X-ray crystallographic and cryo-EM structures, as well as thermodynamic analysis of human EAAT1 in different ion bound conformations, including elusive counter-transport ion bound states. Binding energies of Na and H , and unexpectedly Ca , are coupled to neurotransmitter binding. Ca competes for a conserved Na site, suggesting a regulatory role for Ca in glutamate transport at the synapse, while H binds to a conserved glutamate residue stabilizing substrate occlusion. The counter-transported ion binding site overlaps with that of glutamate, revealing the K -based mechanism to exclude the transmitter during the transport cycle and to prevent its neurotoxic release on the extracellular side.
詳細: Gctf / タイプ: PHASE FLIPPING AND AMPLITUDE CORRECTION
粒子像の選択
選択した粒子像数: 2298481
対称性
点対称性: C3 (3回回転対称)
3次元再構成
解像度: 3.99 Å / 解像度の算出法: FSC 0.143 CUT-OFF / 粒子像の数: 34433 / クラス平均像の数: 1 / 対称性のタイプ: POINT
原子モデル構築
プロトコル: RIGID BODY FIT / 空間: REAL 詳細: For model building, the scaD and tranD of Rb+/Ba2+ bound X-ray structure were fitted into the EM map as separate rigid-bodies using Chimera.