Nucleoside transporter proteins of Saccharomyces cerevisiae -: Demonstration of a transporter (FUI1) with high uridine selectivity in plasma membranes and a transporter (FUN26) with broad nucleoside selectivity in intracellular membranes
Nucleoside transporter proteins of Saccharomyces cerevisiae -: Demonstration of a transporter (FUI1) with high uridine selectivity in plasma membranes and a transporter (FUN26) with broad nucleoside selectivity in intracellular membranes
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DOI：
10.1074/jbc.m000239200
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发表时间：
2000-08-25
影响因子：
4.8
通讯作者：
Cass, CE
中科院分区：
文献类型：
--
作者：
Vickers, MF;Yao, SYM;Cass, CE
FUI 1和功能未知26（FUN 26）是功能不确定的蛋白质，分别与转运蛋白的尿嘧啶/尿囊素通透酶和平衡型核苷转运蛋白家族的成员具有序列相似性，[H-3]尿苷内流通过破坏编码FUI 1（fui 1）的基因而消除，并通过表达FUI 1 cDNA而恢复，而在有转运能力的酵母和完全阴性的酵母中，FUN26基因的破坏或FUN26 cDNA的过表达分别不影响内流，FUI 1以高亲和力转运尿苷（K-m，22 +/-3 μ M），并且不受高浓度（1 mM）的各种核糖和脱氧核糖核苷或核碱基的影响或仅部分抑制。当FUN26 cDNA在非洲爪蟾卵母细胞中表达时，[H-3]尿苷，[H-3]腺苷和[H-3]胞苷的内向通量受到刺激，尿苷内流不受pH的影响，也不受地拉卓，双嘧达莫或硝基苄基巯基嘌呤核糖核苷的抑制。含有免疫标记的重组FUN 26（显示在卵母细胞中有功能）的酵母膜的分级分离证明该蛋白主要在细胞内膜中。这些结果表明FUI 1对含尿嘧啶的核糖核苷具有高选择性，并通过细胞表面膜输入尿苷，而FUN 26具有广泛的核苷选择性，最有可能的功能是通过细胞内膜运输核苷。
FUI1 and function unknown now 26 (FUN26) are proteins of uncertain function with sequence similarities to members of the uracil/allantoin permease and equilibrative nucleoside transporter families of transporter proteins, respectively, [H-3]Uridine influx was eliminated by disruption of the gene encoding FUI1 (fui1) and restored by expression of FUI1 cDNA, whereas influx in transport-competent and full-negative yeast were unaffected, respectively, by disruption of the FUN26 gene or overexpression of FUN26 cDNA, FUI1 transported uridine with high affinity (K-m, 22 +/- 3 mu M) and was unaffected or inhibited only partially by high concentrations (1 mM) Of a variety of ribo- and deoxyribonucleosides or nucleobases. When FUN26 cDNA was expressed in oocytes of Xenopus laevis, inward fluxes of [H-3]uridine, [H-3]adenosine, and [H-3]cytidine were stimulated, and uridine influx was independent of pH and not inhibited by dilazep, dipyridamole, or nitrobenzylmercaptopurine ribonucleoside. Fractionation of yeast membranes containing immunotagged recombinant FUN26 (shown to be functional in oocytes) demonstrated that the protein was primarily in intracellular membranes. These results indicated that FUI1 has high selectivity for uracil-containing ribonucleosides and imports uridine across cell-surface membranes, whereas FUN26 has broad nucleoside selectivity and most likely functions to transport nucleosides across intracellular membranes.