Functional analysis and molecular model of the human urate transporter/channel, hUAT.
Functional analysis and molecular model of the human urate transporter/channel, hUAT.
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DOI：
10.1152/ajprenal.00333.2001
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发表时间：
2002-07
期刊：
影响因子：
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通讯作者：
E. Leal-Pinto;B. Cohen;M. Lipkowitz;R. Abramson
中科院分区：
文献类型：
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作者：
E. Leal-Pinto;B. Cohen;M. Lipkowitz;R. Abramson
重组蛋白，命名为hUAT，大鼠尿酸盐转运蛋白/通道（UAT）的人类同源物，作为脂质双层中的高选择性尿酸盐通道。功能分析表明，hUAT活性，如UAT，选择性地阻断oxonate从其胞质侧，而吡嗪酸和腺苷选择性地阻断从通道的细胞外面。重要的是，hUAT是半乳糖凝集素，一种具有两个结合乳糖的β-半乳糖苷结合结构域的蛋白质。乳糖显著增加hUAT开放概率，但仅当添加到通道的细胞外侧时。这种对开放概率的影响被葡萄糖而不是核糖模仿，表明细胞外葡萄糖在调节hUAT通道活性中的作用。这些功能的观察支持一个四跨膜结构域的结构模型的人尿嘧啶核苷，如先前预测的UAT的一级结构。然而，hUAT和UAT在功能上并不相同：hUAT具有显著较低的单通道电导，并且开路概率与电压无关。这些差异表明，在这些高度同源的蛋白质中特定氨基酸的进化变化在定义这些生物物理特性方面具有功能相关性。
Recombinant protein, designated hUAT, the human homologue of the rat urate transporter/channel (UAT), functions as a highly selective urate channel in lipid bilayers. Functional analysis indicates that hUAT activity, like UAT, is selectively blocked by oxonate from its cytosolic side, whereas pyrazinoate and adenosine selectively block from the channel's extracellular face. Importantly, hUAT is a galectin, a protein with two beta-galactoside binding domains that bind lactose. Lactose significantly increased hUAT open probability but only when added to the channel's extracellular side. This effect on open probability was mimicked by glucose, but not ribose, suggesting a role for extracellular glucose in regulating hUAT channel activity. These functional observations support a four-transmembrane-domain structural model of hUAT, as previously predicted from the primary structure of UAT. hUAT and UAT, however, are not functionally identical: hUAT has a significantly lower single-channel conductance and open probability is voltage independent. These differences suggest that evolutionary changes in specific amino acids in these highly homologous proteins are functionally relevant in defining these biophysical properties.