A Leishmania major nucleobase transporter responsible for allopurinol uptake is a functional homolog of the Trypanosoma brucei H2 transporter
A Leishmania major nucleobase transporter responsible for allopurinol uptake is a functional homolog of the Trypanosoma brucei H2 transporter
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DOI：
10.1124/mol.63.4.814
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发表时间：
2003-04-01
影响因子：
3.6
通讯作者：
De Koning, HP
中科院分区：
文献类型：
--
作者：
Al-Salabi, MI;Wallace, LJM;De Koning, HP
核碱基转运体在原生动物寄生虫的生理中起着重要的作用，因为这些生物是嘌呤营养不良者，完全依赖于这些重要化合物的回收。嘌呤转运体也被证明介导重要抗寄生虫药物的摄取。在目前的研究中，我们研究了利什曼原虫对[H-3]腺嘌呤、[H-3]次黄嘌呤-和[H-3]别嘌呤醇（一种抗利什曼原虫次黄嘌呤类似物）的摄取。这些化合物均由一个高亲和转运体Lm-NBT1携带，其K-m值分别为4.6 +/- 0.9、0.71 +/- 0.07和54 +/- 3 muM。鸟嘌呤和黄嘌呤完全抑制[H-3]腺嘌呤转运，K-i值分别为2.8 +/- 0.7和23 +/- 8 muM。利用嘌呤类似物，获得了LmNBT1的抑制剂谱，从而可以构建转运体结合位点与渗透物之间相互作用的定量模型。该模型预测次黄嘌呤通过氢键与嘌呤环的N(1)H、N3、N7和N(9)H结合，总吉布斯自由能为-39.5 kJ/mol。与腺嘌呤的相互作用相似，除了与N1有一个弱氢键（在腺嘌呤中未质子化）。Lm-NBT1与布鲁氏锥虫H2 （TbH2）转运体的预测底物结合模式几乎相同。我们提出它们各自结合位点的结构非常相似，LmNBT1可以被命名为TbH2的功能同源物。
Nucleobase transporters play an important role in the physiology of protozoan parasites, because these organisms are purine auxotrophs and rely entirely on salvage of these vital compounds. Purine transporters have also been shown to mediate the uptake of important antiparasitic drugs. In the current study, we investigated the uptake of [H-3]adenine, [H-3]hypoxanthine- and [H-3]allopurinol, an antileishmanial hypoxanthine analog by Leishmania major. These compounds were all taken up by a single high-affinity transporter, Lm-NBT1, with K-m values of 4.6 +/- 0.9, 0.71 +/- 0.07, and 54 +/- 3 muM, respectively. Guanine and xanthine fully inhibited [H-3]adenine transport, with K-i values of 2.8 +/- 0.7 and 23 +/- 8 muM. Using purine analogs, an inhibitor profile for LmNBT1 was obtained, which allowed the construction of a quantitative model for the interactions between the transporter binding site and the permeant. The model predicts that hypoxanthine was bound through hydrogen bonds to N(1)H, N3, N7, and N(9)H of the purine ring, with a total Gibbs free energy of -39.5 kJ/mol. The interactions with adenine were similar, except for a weak hydrogen bond to N1 (unprotonated in adenine). The predicted mode of substrate binding for Lm-NBT1 was almost identical to that for the Trypanosoma brucei H2 (TbH2) transporter. It is proposed that the architecture of their respective binding sites is very similar and that LmNBT1 can be named a functional homolog of TbH2.