MOLECULAR MECHANISM OF RENAL NA+ DEPENDENT COTRANSPORT

描述(改编自申请人的摘要)：长期 该项目的目标是确定结构如何 钠依赖共转运蛋白决定了它们的功能特性。 当前提议的重点是在分子水平上表征 肾近端小管Na+/二羧酸共转运体。这些 转运蛋白对肾脏的功能非常重要。 Krebs循环中间体的重吸收，并在酸碱中发挥作用 平衡和有机阴离子排泄。刷子边界的Na+/二羧酸盐 辅转运蛋白在肾结石的发生发展中起重要作用。 调节尿中柠檬酸浓度。首席调查员 最近克隆了一种兔肾Na+/二羧酸盐并进行了序列测定 共转运蛋白，NADC-1和人类同源基因，hNaDC-1。NADC-1似乎 与刷子的低亲和力Na+/二羧酸共转运体相对应 边界膜。这项研究的第一个具体目标是确定 组氨酸-106在NADC-1和NADC-1转运琥珀酸中的作用 HNaDC-1。第二个具体目标是确定结构域或残基。 参与底物的选择性和结合，通过制备嵌合体 相关的运输商。第三个具体目标是克隆肾高 亲和Na+/二羧酸共转运蛋白。这辆运输车将被用来 鉴定对高亲和力底物结合重要的残基。这些 研究应提供有关功能性质的基本信息 这一家族的钠依赖转运蛋白，以及生理上的 这些转运蛋白在肾脏中的作用。

DESCRIPTION (Adapted from the Applicant's Abstract): The long-term objective of this project is to determine how the structures of sodium-dependent cotransport proteins determine their functional properties. The focus of the current proposal is to characterize at the molecular level the Na+/dicarboxylate cotransporters of the renal proximal tubule. These transporters are important to the function of the kidney in their reabsorption of Krebs cycle intermediates, and play a role in acid-base balance and organic anion excretion. The brush border Na+/dicarboxylate cotransporter has been implicated in the development of kidney stones by its regulation of urinary citrate concentrations. The principal investigator has recently cloned and sequenced a rabbit renal Na+/dicarboxylate cotransporter, NaDC-1 and the human homolog, hNaDC-1. NaDC-1 appears to correspond to the low affinity Na+/dicarboxylate cotransporter of the brush border membrane. The first Specific Aim of this study is to determine the role that histidine-106 plays in the transport of succinate by NaDC-1 and hNaDC-1. The second Specific Aim is to identify domains or residues involved in substrate selectivity and binding, by preparing chimeras between related transporters. The third Specific Aim is to clone the renal high affinity Na+/dicarboxylate cotransporter. This transporter will be used to identify residues important for high affinity substrate binding. These studies should provide fundamental information on the functional properties of this family of sodium-dependent transporters, and on the physiological role of these transporters in the kidney.