Glutamate is the main excitatory transmitter in the mammalian central nervous system; glutamate transporters keep the synaptic glutamate concentrations at bay for normal brain function. Arachidonic acid (AA), docosahexaenoic acid (DHA), and other unsaturated fatty acids modulate glutamate transporters in cell- and tissue slices-based studies. Here, we investigated their effect and mechanism using a purified archaeal glutamate transporter homolog reconstituted into the lipid membranes. AA, DHA, and related fatty acids irreversibly inhibited the sodium-dependent concentrative substrate uptake into lipid vesicles within the physiologically relevant concentration range. In contrast, AA did not inhibit amino acid exchange across the membrane. The length and unsaturation of the aliphatic tail affect inhibition, and the free carboxylic headgroup is necessary. The inhibition potency did not correlate with the fatty acid effects on the bilayer deformation energies. AA does not affect the conformational dynamics of the protein, suggesting it does not inhibit structural transitions necessary for transport. Single-transporter and membrane voltage assays showed that AA and related fatty acids mediate cation leak, dissipating the driving sodium gradient. Thus, such fatty acids can act as cation ionophores, suggesting a general modulatory mechanism of membrane channels and ion-coupled transporters.

中文翻译：

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游离脂肪酸通过消散离子梯度来抑制离子偶联膜转运蛋白。


谷氨酸是哺乳动物中枢神经系统中的主要兴奋性递质;谷氨酸转运蛋白保持突触谷氨酸浓度，以实现正常的大脑功能。花生四烯酸 （AA）、二十二碳六烯酸 （DHA） 和其他不饱和脂肪酸在基于细胞和组织切片的研究中调节谷氨酸转运蛋白。在这里，我们使用重构到脂质膜中的纯化古细菌谷氨酸转运蛋白同源物研究了它们的作用和机制。AA 、 DHA 和相关脂肪酸在生理相关浓度范围内不可逆地抑制钠依赖性浓缩底物摄取到脂质囊泡中。相比之下，AA 不抑制跨膜的氨基酸交换。脂肪族尾部的长度和不饱和度会影响抑制，游离羧基是必要的。抑制效力与脂肪酸对双层变形能的影响无关。AA 不影响蛋白质的构象动力学，表明它不会抑制运输所需的结构转变。单转运蛋白和膜电压测定表明，AA 和相关脂肪酸介导阳离子泄漏，消散驱动钠梯度。因此，这种脂肪酸可以充当阳离子离子载体，表明膜通道和离子偶联转运蛋白的一般调节机制。