A two-domain elevator mechanism for sodium/proton antiport.
A two-domain elevator mechanism for sodium/proton antiport.
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作者：
钠/质子(Na+/H+)逆向转运蛋白位于每个细胞的质膜上，对细胞内环境的稳定起着至关重要的作用。在人类中，它们的功能障碍与高血压、心力衰竭和癫痫等疾病有关，它们是公认的药物靶点。最好理解的Na+/H+反向转运的模型系统是来自大肠杆菌的NaA，其中EM和晶体结构都是可用的。NhaA由两个不同的结构域组成，一个是核心区，一个是二聚结构域。在nhaA晶体结构中，在两个结构域之间有一个空腔，提供从蛋白质向内表面进入离子结合位置的途径。像许多Na+/H+逆向转运蛋白一样，NhaA的活性受到pH的调节，只有在pH 6.5以上才变得活跃，在那里人们认为发生了构象变化。到目前为止，唯一报道的NhaA晶体结构是低pH灭活形式。在这里，我们描述了来自Thermus thermophilus的Na+/H+逆向转运蛋白NapA的3？分辨率的活性结构，它是从pH 7.8的晶体中分解出来的。在NAPA结构中，核心和二聚结构域与NHAA中看到的位置不同，一个带负电荷的空腔现在已经向外开放。胞外腔允许进入一个严格保守的天冬氨酸残基，被认为直接协调离子结合，这一作用在这里得到了分子动力学模拟的支持。然而，要交替访问这个离子结合位点，需要核心域惊人地大旋转，大约与二聚界面成20°。我们得出的结论是，尽管Na+/H+逆向转运蛋白的快速转运速率高达1500离子/秒，但它们是按照两个区域的摇摆束模型运行的，揭示了与次级活性转运蛋白相关的主题。
Sodium/proton (Na+/H+) antiporters, located at the plasma membrane in every cell, are vital for cell homeostasis. In humans, their dysfunction has been linked to diseases, such as, hypertension, heart failure and epilepsy and they are well-established drug targets. The best understood model system for Na+/H+ antiport is NhaA from Escherichia coli, where both EM and crystal structures are available. NhaA is made up of two distinct domains, a Core domain and a Dimerisation domain. In the NhaA crystal structure a cavity is located between the two domains providing access to the ion-binding site from the inward-facing surface of the protein. Like many Na+/H+ antiporters, the activity of NhaA is regulated by pH, only becoming active above pH 6.5, where a conformational change is thought to occur. To date, the only reported NhaA crystal structure is of the low pH inactivated form. Here, we describe the active-state structure of a Na+/H+ antiporter, NapA from Thermus thermophilus at 3 Å resolution, solved from crystals grown at pH 7.8. In the NapA structure, the Core and Dimerisation domains are in different positions to those seen in NhaA and a negatively charged cavity has now opened to the outside. The extracellular cavity allows access to a strictly conserved aspartate residue thought to directly coordinate ion-binding, a role supported here by molecular dynamics simulations. To alternate access to this ion-binding site, however, requires a surprisingly large rotation of the Core domain, some 20° against the Dimerisation interface. We conclude that despite their fast transport rates of up to 1500 ions/sec, Na+/H+ antiporters operate by a two-domain rocking bundle model, revealing themes relevant to secondary-active transporters in general.
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影响因子：
5.5
作者：
Hess, Berk;Kutzner, Carsten;Lindahl, Erik
通讯作者：
Lindahl, Erik
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
14.8
作者：
Drew, David;Newstead, Simon;Iwata, So
通讯作者：
Iwata, So
影响因子：
5.5
作者：
Hess, Berk
通讯作者：
Hess, Berk
DOI：
10.1107/s0907444909052925
发表时间：
2010-02
期刊：
Acta crystallographica. Section D, Biological crystallography
影响因子：
--
作者：
Adams PD;Afonine PV;Bunkóczi G;Chen VB;Davis IW;Echols N;Headd JJ;Hung LW;Kapral GJ;Grosse-Kunstleve RW;McCoy AJ;Moriarty NW;Oeffner R;Read RJ;Richardson DC;Richardson JS;Terwilliger TC;Zwart PH
通讯作者：
Zwart PH