L amino acid transporter structure and molecular bases for the asymmetry of substrate interaction
L amino acid transporter structure and molecular bases for the asymmetry of substrate interaction
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DOI：
10.1038/s41467-019-09837-z
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发表时间：
2019-04-18
影响因子：
16.6
通讯作者：
Palacin, Manuel
中科院分区：
文献类型：
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作者：
Errasti-Murugarren, Ekaitz;Fort, Joana;Palacin, Manuel
L-氨基酸转运蛋白 (LAT) 在人类生理学中发挥着关键作用，并与多种人类病理有关。 LAT 是不对称氨基酸交换剂，其中低表观亲和力的细胞质侧控制在细胞外侧具有高表观亲和力的底物的交换。在这里，我们报告了 LAT（细菌丙氨酸-丝氨酸-半胱氨酸交换器（BasC））的晶体结构，其在载脂蛋白和底物结合状态下均处于非闭塞向内构象。我们将 BasC 与纳米体复合物结晶，纳米体从细胞内侧阻断转运蛋白，从而揭示了 BasC 底物相互作用的侧面。人类 LAT 中的两个保守残基 Tyr 236 和 Lys 154 位于与钠依赖性 APC 超家族转运蛋白的 Na1 和 Na2 位点相同的位置。功能研究和分子动力学 (MD) 计算表明，这些残基是 BasC 和同源人类转运蛋白 Asc-1 中不对称底物相互作用的关键。
L-amino acid transporters (LATs) play key roles in human physiology and are implicated in several human pathologies. LATs are asymmetric amino acid exchangers where the low apparent affinity cytoplasmic side controls the exchange of substrates with high apparent affinity on the extracellular side. Here, we report the crystal structures of an LAT, the bacterial alanine-serine-cysteine exchanger (BasC), in a non-occluded inward-facing conformation in both apo and substrate-bound states. We crystallized BasC in complex with a nanobody, which blocks the transporter from the intracellular side, thus unveiling the sidedness of the substrate interaction of BasC. Two conserved residues in human LATs, Tyr 236 and Lys 154, are located in equivalent positions to the Na1 and Na2 sites of sodium-dependent APC superfamily transporters. Functional studies and molecular dynamics (MD) calculations reveal that these residues are key for the asymmetric substrate interaction of BasC and in the homologous human transporter Asc-1.