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Cryo-EM structure of the human NKCC1 transporter reveals mechanisms of ion coupling and specificity
The EMBO Journal ( IF 11.4 ) Pub Date : 2022-10-14 , DOI: 10.15252/embj.2021110169
Caroline Neumann 1, 2 , Lena Lindtoft Rosenbaek 3 , Rasmus Kock Flygaard 1, 2 , Michael Habeck 1, 2 , Jesper Lykkegaard Karlsen 2 , Yong Wang 4, 5 , Kresten Lindorff-Larsen 4 , Hans Henrik Gad 2 , Rune Hartmann 2 , Joseph Anthony Lyons 1, 2, 6 , Robert A Fenton 3 , Poul Nissen 1, 2
Affiliation  

The sodium–potassium–chloride transporter NKCC1 of the SLC12 family performs Na+-dependent Cl- and K+-ion uptake across plasma membranes. NKCC1 is important for regulating cell volume, hearing, blood pressure, and regulation of hyperpolarizing GABAergic and glycinergic signaling in the central nervous system. Here, we present a 2.6 Å resolution cryo-electron microscopy structure of human NKCC1 in the substrate-loaded (Na+, K+, and 2 Cl) and occluded, inward-facing state that has also been observed for the SLC6-type transporters MhsT and LeuT. Cl binding at the Cl1 site together with the nearby K+ ion provides a crucial bridge between the LeuT-fold scaffold and bundle domains. Cl-ion binding at the Cl2 site seems to undertake a structural role similar to conserved glutamate of SLC6 transporters and may allow for Cl-sensitive regulation of transport. Supported by functional studies in mammalian cells and computational simulations, we describe a putative Na+ release pathway along transmembrane helix 5 coupled to the Cl2 site. The results provide insight into the structure–function relationship of NKCC1 with broader implications for other SLC12 family members.

中文翻译:

人类 NKCC1 转运蛋白的冷冻电镜结构揭示了离子耦合和特异性的机制

SLC12 家族的钠钾氯化物转运蛋白 NKCC1 执行 Na +依赖性 Cl - - 和 K +离子跨质膜摄取。NKCC1 对于调节细胞体积、听力、血压以及调节中枢神经系统中的超极化 GABA 能和甘氨酸能信号非常重要。在这里,我们展示了人类 NKCC1 的 2.6 Å 分辨率冷冻电子显微镜结构,该结构处于载有底物(Na +、K +和 2 Cl -)和封闭的向内状态,这也已在 SLC6 型中观察到转运蛋白 MhsT 和 LeuT。Cl −与附近的 K +结合在 Cl1 位点离子在 LeuT 折叠支架和束结构域之间提供了重要的桥梁。Cl -离子在 Cl2 位点的结合似乎承担了类似于 SLC6 转运蛋白的保守谷氨酸的结构作用,并且可能允许对 Cl -敏感的转运调节。在哺乳动物细胞功能研究和计算模拟的支持下,我们描述了沿着跨膜螺旋 5 与 Cl2 位点偶联的假定 Na +释放途径。结果提供了对 NKCC1 的结构-功能关系的深入了解,并对其他 SLC12 家族成员具有更广泛的意义。
更新日期:2022-10-14
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