Thallium ions can replace both sodium and potassium ions in the glutamate transporter excitatory amino acid carrier 1.
Thallium ions can replace both sodium and potassium ions in the glutamate transporter excitatory amino acid carrier 1.
复制标题
铊离子可以替代谷氨酸转运蛋白兴奋性氨基酸载体1中的钠离子和钾离子。
DOI：
10.1021/bi8017174
复制
发表时间：
2008
期刊：
影响因子：
2.9
通讯作者：
Grewer,Christof
中科院分区：
文献类型：
--
作者：
Tao,Zhen;Gameiro,Armanda;Grewer,Christof
兴奋性氨基酸载体EAAC 1属于谷氨酸转运蛋白家族，其使用钠和钾的电化学跨膜梯度来介导谷氨酸向细胞中的上坡转运。虽然阳离子与EAAC 1相互作用的位点是未知的，但在细菌谷氨酸转运蛋白同系物GltPh的晶体结构中观察到两个阳离子结合位点。尽管在晶体结构中被Tl+占据，但这些位点被认为是Na+结合位点。因此，我们测试了Tl+是否也具有在哺乳动物转运蛋白中替代Na+的能力。我们的数据表明，T1+可以以高亲和力结合EAAC1，并介导多种不同的功能。当施加到细胞质时，Tl+可以在功能上替代钾，并且可以支持谷氨酸转运电流。当在细胞外应用时，Tl+诱导一些模仿Na+结合的转运蛋白的行为，例如阳离子诱导的阴离子电导的激活和底物结合位点的产生，但它不能代替Na+支持谷氨酸转运电流。此外，我们的数据显示了两个酸性氨基酸的突变可能涉及阳离子结合（D367和D454）对Na+和Tl+亲和力的差异效应。总体而言，我们的研究结果表明，谷氨酸转运蛋白与Tl+相互作用的能力是保守的GltPh和哺乳动物成员的转运蛋白家族。然而，与不结合K+的GltPh相反，当与哺乳动物蛋白质相互作用时，Tl+在模拟K+方面比Na+更有效。
The excitatory amino acid carrier EAAC1 belongs to a family of glutamate transporters that use the electrochemical transmembrane gradients of sodium and potassium to mediate uphill transport of glutamate into the cell. While the sites of cation interaction with EAAC1 are unknown, two cation binding sites were observed in the crystal structure of the bacterial glutamate transporter homologue GltPh. Although occupied by Tl+in the crystal structure, these sites were proposed to be Na+binding sites. Therefore, we tested whether Tl+has the ability to replace Na+also in the mammalian transporters. Our data demonstrate that Tl+can bind to EAAC1 with high affinity and mediate a host of different functions. Tl+can functionally replace potassium when applied to the cytoplasm and can support glutamate transport current. When applied extracellularly, Tl+induces some behavior that mimics that of the Na+-bound transporter, such as activation of the cation-induced anion conductance and creation of a substrate binding site, but it cannot replace Na+in supporting glutamate transport current. Moreover, our data show a differential effect of mutations to two acidic amino acids potentially involved in cation binding (D367 and D454) on Na+and Tl+affinity. Overall, our results demonstrate that the ability of the glutamate transporters to interact with Tl+is conserved between GltPh and a mammalian member of the transporter family. However, in contrast to GltPh, which does not bind K+, Tl+is more efficient in mimicking K+than Na+when interacting with the mammalian protein.