Organic anion transporters (OATs) of the SLC22 family have crucial roles in the transport of organic anions, including metabolites and therapeutic drugs, and in transporter-mediated drug-drug interactions. In the kidneys, OATs facilitate the elimination of metabolic waste products and xenobiotics. However, their transport activities can lead to the accumulation of certain toxic compounds within cells, causing kidney damage. Moreover, OATs are important drug targets, because their inhibition modulates the elimination or retention of substrates linked to diseases. Despite extensive research on OATs, the molecular basis of their substrate and inhibitor binding remains poorly understood. Here we report the cryo-EM structures of rat OAT1 (also known as SLC22A6) and its complexes with para-aminohippuric acid and probenecid at 2.1, 2.8 and 2.9 Å resolution, respectively. Our findings reveal a highly conserved substrate binding mechanism for SLC22 transporters, wherein four aromatic residues form a cage to accommodate the polyspecific binding of diverse compounds.

SLC22 家族的有机阴离子转运蛋白 （OAT） 在有机阴离子（包括代谢物和治疗药物）的转运以及转运蛋白介导的药物相互作用中起着至关重要的作用。在肾脏中，OAT 有助于消除代谢废物和外源性物质。然而，它们的运输活动会导致某些有毒化合物在细胞内积累，从而导致肾脏损伤。此外，OAT 是重要的药物靶点，因为它们的抑制调节与疾病相关的底物的消除或保留。尽管对 OAT 进行了广泛的研究，但对其底物和抑制剂结合的分子基础仍然知之甚少。在这里，我们分别以 2.1、2.8 和 2.9 Å 的分辨率报道了大鼠 OAT1 （也称为 SLC22A6） 及其与对氨基马尿酸和丙磺舒的复合物的冷冻电镜结构。我们的研究结果揭示了 SLC22 转运蛋白的高度保守的底物结合机制，其中四个芳香族残基形成一个笼子，以适应不同化合物的多特异性结合。