Specific Interdomain Synergy in the UapA Transporter Determines Its Unique Specificity for Uric Acid among NAT Carriers
Specific Interdomain Synergy in the UapA Transporter Determines Its Unique Specificity for Uric Acid among NAT Carriers
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DOI：
10.1016/j.jmb.2008.08.005
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发表时间：
2008-10-24
影响因子：
5.6
通讯作者：
Diallinas, George
中科院分区：
文献类型：
--
作者：
Papageorgiou, Loannis;Gournas, Christos;Diallinas, George
UapA 是构巢曲霉的一种尿酸-黄嘌呤渗透酶，已被用作原型来研究普遍存在的核碱基-抗坏血酸转运蛋白 (NAT) 家族中的结构-功能关系。利用新颖的遗传筛选、合理的突变设计、嵌合 NAT 分子和广泛的转运动力学分析，我们表明跨膜片段 (TMS)1、TMS8-9 环和 TMS12 三个不同结构域之间的动态协同作用定义了 UapA 的功能和特异性。 TMS8-9 环包含四个对于底物结合和转运绝对必需的残基（Glu356、Asp388、Gln408 和 Asn409），而 TMS1. TMS12 似乎通过空间位阻或静电排斥来控制嘌呤对 TMS8-9 结构域的差异访问。因此，UapA 特异性直接由给定底物与 TMS8-9 环的特异性相互作用决定，间接由该环与 TMS1 和 TMS12 的相互作用决定。我们最终表明，UapA 结构域之间的分子内协同作用具有高度特异性，并提出它构成了 UapA 对尿酸的独特特异性进化的基础，而其他 NAT 成员中不存在这种特性。 (C) 2008 Elsevier Ltd. 保留所有权利。
UapA, a uric acid-xanthine permease of Aspergillus nidulans, has been used as a prototype to study structure-function relationships in the ubiquitous nucleobase-ascorbate transporter (NAT) family. Using novel genetic screens, rational mutational design, chimeric NAT molecules, and extensive transport kinetic analyses, we show that dynamic synergy between three distinct domains, transmembrane segment (TMS)1, the TMS8-9 loop, and TMS12, defines the function and specificity of UapA. The TMS8-9 loop includes four residues absolutely essential for substrate binding and transport (Glu356, Asp388, Gln408, and Asn409), whereas TMS1. and TMS12 seem to control, through steric hindrance or electrostatic repulsion, the differential access of purines to the TMS8-9 domain. Thus, UapA specificity is determined directly by the specific interactions of a given substrate with the TMS8-9 loop and indirectly by interactions of this loop with TMS1 and TMS12. We finally show that intramolecular synergy among UapA domains is highly specific and propose that it forms the basis for the evolution of the unique specificity of UapA for uric acid, a property not present in other NAT members. (C) 2008 Elsevier Ltd. All rights reserved.