The role of membrane lipids in modulating eukaryotic transporter assembly and function remains unclear. We investigated the effect of membrane lipids in the structure and transport activity of the purine transporter UapA fromAspergillus nidulans. We found that UapA exists mainly as a dimer and that two lipid molecules bind per UapA dimer. We identified three phospholipid classes that co-purified with UapA: phosphatidylcholine, phosphatidylethanolamine (PE), and phosphatidylinositol (PI). UapA delipidation caused dissociation of the dimer into monomers. Subsequent addition of PI or PE rescued the UapA dimer and allowed recovery of bound lipids, suggesting a central role of these lipids in stabilizing the dimer. Molecular dynamics simulations predicted a lipid binding site near the UapA dimer interface. Mutational analyses established that lipid binding at this site is essential for formation of functional UapA dimers. We propose that structural lipids have a central role in the formation of functional, dimeric UapA.

中文翻译：

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结构脂质使真核嘌呤转运蛋白UapA的功能性寡聚体的形成。

膜脂质在调节真核转运蛋白组装和功能中的作用尚不清楚。我们调查了膜脂质对来自构巢曲霉的嘌呤转运蛋白UapA的结构和转运活性的影响。我们发现UapA主要以二聚体形式存在，每个UapA二聚体结合两个脂质分子。我们确定了与UapA共同纯化的三种磷脂类别：磷脂酰胆碱，磷脂酰乙醇胺（PE）和磷脂酰肌醇（PI）。UapA脱脂导致二聚体分解为单体。随后加入PI或PE可以挽救UapA二聚体并回收结合的脂质，表明这些脂质在稳定二聚体中起着核心作用。分子动力学模拟预测了UapA二聚体界面附近的脂质结合位点。突变分析证实，该位点的脂质结合对于功能性UapA二聚体的形成至关重要。我们提出结构脂质在功能性二聚体UapA的形成中具有核心作用。